Brythonic Personal Names

The list below includes names taken from early Brythonic sources and those still used in Wales, Brittany and Cornwall today.

All forms have been standardised according to modern Welsh orthography, except modern Breton and Cornish forms, which are coloured blue and green respectively. Old Breton and Cornish forms with no modern equivalent have been given in standard modern Welsh and are marked with an asterisk (*).

Early sources used:

bgg	Bonedd Gwŷr y Gogledd, MS 13th C., possibly from 12th C. source
bm	Bodmin Manumissions, 9th - 10th C.
hg	Harleian Genealogies, MS c12th C., possibly from 10th C. material
t	Welsh Triads, late 13th C.
yg	Y Gododdin, late 13th C. possibly from much earlier material.

Aeddan	MW. Ædan, Aedan, OC. Aedan, E. Aidan. A borrowing from OI. Aedán (I. Aodhán), meaning 'little fire'. hg, bm, bgg, yg
Angharad	(f.) Br. Ancaratā 'well loved' (W. caraf* 'I love').
Anarawd	MW. Anarant (sic.). Probably from L. Honōrātus meaning 'distinguished'. hg
Anaostl*	(f.) OC. Anaguistl. Probably 'wealth hostage' with W. anaw 'wealth; wealthy' and gwystl 'hostage'. bm
Aneirin	MW. Aneurin, Aneirin. Of uncertain origin. Perhaps from L. Nigrīnus < niger 'black', or Br. Nagrīnos, a derivative of PC. nagro- (OI. nár 'noble, honourable; modest', náire 'shame, bashfulness, modesty, decorum'). yg
Anthun	E. Anthony. From L. Antōnius. hg
Arc'hantael	(f.). B. arc'hant 'silver' and ael 'eyebrow'.
Artan, Arthan	MW. Artan. Probably a borrowing from OI. Artán 'little bear', but it may be the Welsh cognate *Arthan. hg
Arthek	Br. Artācos 'bear-like' (W. arth* 'bear').
Arthfoddw	MW. Artbodgu. Br. Artobodwos 'bear crow' (W. arth* 'bear', OI. bodb, badb 'hooded crow'). hg
Arthial	MW. Arthgal, I. Árdal. From PC. Artogalos 'bear power' (W. arth* 'bear', gallaf 'I am able'). hg
Arthien	MW. Arthgen. From Br. Artogenos 'bear-born' (W. arth* 'bear'). hg
Arthur	B. Arzhur. Probably the most famous Brythonic name, but of uncertain origin. Probably from L. Artōrius. hg, t, YG
Asa, Asaph	MW. Assa. Probably the Biblical names Asa or Asaph. bs
Awen	(f.) The common noun W. awen 'inspiration, muse', perhaps related to awel 'breeze'.
Baglan	MW. Baglan. W. baglan 'crook, crutch' from bagl 'crosier, crook'. bs
Bedwyr	E. Bedivere. Probably Br. Betwowiros 'birch man' (W. bedwen* 'birch tree', gŵr 'man'). t
Beli	MW. Beli, OC. Beli. Of uncertain origin, though a relatively common name in the king lists. Perhaps from Br. Bolgjos, Belgjos < PC. bolg- 'belly' (W. bola), or a name relating to the god Belenos. hg, bm, yg, t, bs
Berwyn	MW. Berwin. Br. Barrowindos 'white top' (W. bar* 'summit, top, crest', gwyn 'white'). jc
Bizouarn	OB. Budhoiarn. From B. buz 'profit' (previously 'victory') and houarn 'iron'.
Bleiddfan	MW. Bleidvan. Br. Bledjomandus 'wolf pony' (W. blaidd* 'wolf'). yg
Bleiddgwn*	OC. Bleidcum (sic.). Br. Bledjocunam (acc.) 'wolf hound' (C. bleydh* 'wolf', ki 'dog'). bm
Bleiddig	From W. blaidd 'wolf' and the diminutive -ig. yg
Bleiddudd	MW. Bleydiud, Bleiddut, OC. Bleidiud. From Br. Bledjojüd- 'wolf lord' (W. blaidd* 'wolf', udd 'lord'). hg, bm, bs
Bodgad	MW. Botgat. Br. *Bodwocatus 'battle crow' (OI. bodb, badb 'hooded crow', W. cad 'battle').yg
Boddw	MW. Bodgu. Br. bodwo- 'crow' (OI. bodb, badb* 'hooded crow'). hg, yg
Bradwen	MW. Bratwen. Seemingly a compound of W. brad 'treachery, treason' and gwen 'white'. yg
Brân	MW. Bran. Br. Branos 'crow, raven' (W. brân* 'crow', OI. bran 'raven'), a bird commonly associated with battles. hg, t
Branek	From Br. Branācos 'raven-like' (C. bran* 'crow')
Breichiol	MW. Brechiaul. Possibly L. Bracchiālis < bracchium 'arm' (W. braich 'arm, branch'), perhaps inferring 'having strong arms'. There is a Welsh word breichiol 'linked together; brachial'. hg, yg
Brengi*	OC. Brenci. Probably Br. Branocī 'raven hound' (C. bran* 'crow', ki 'dog'). bm
Briog	OC. Frioc, C. Bryok, B. Brieg. Br. Brīgācos 'powerful, esteemed' (C. bri* 'distinction, esteem, importance'). bm
Brochfael	MW. Brochmail, Brocmayl. Br. Broccomaglos 'badger prince' (W. broch* 'badger', mael 'prince, lord'). hg
Bronwen	(f.) Br. Brondowindā 'white breast' (W. bron* 'breast', gwen 'white').
Brezelgar*	OB. Preselgar. The first element is B. brezel 'war' and the second may be B. kar 'friend'.
Brezelgevgant*	OB. Breselcoucant. B. brezel 'war' and the equivalent of W. ceugant 'certain; special'.
Brezelgonan*	OB. Breselconan. B. brezel 'war' and the personal name Br. *Cunagnos (see Cynan).
Brezelvarc'heg*	OB. Breselmarcoc. 'War horseman' from a compound of B. brezel 'war' and marc'heg 'knight'.
Brezelek*	OB. Breseloc. 'Warlike' from Br. Bristelācos (B. brezelek* 'bellicose').
Brythael*	OC. Brithael. Perhaps Br. Britosagelos 'generous of judgment' (C. bres* 'mind, thought', hel 'generous'). bm
Buan	MW. Buan. Probably the common adjective W. buan 'swift, nimble'. bs
Buddfan	MW. Budvan. Br. Büdomandus 'victory pony' (W. budd* 'profit, gain, riches'). yg
Buddug	OC. Budic, OB. Budoc, B. Beuzec E. Boudica. From Br. Büdīcos, Büdīcā 'victorious' (C. budhek* 'victorious', W. buddig 'victorious, successful, generous'). The Breton forms are from equivalent Br. *Büdācos. A female name in Welsh, but apparently masculine in Old Cornish and Old Breton. bm
Buzaret	OB. Buduuoret. B. buz 'profit' (previously 'victory') and gwared 'protection'.
Buzval	OB. Butgual. The first element is B. buz 'profit' (previously 'victory') and the second may be Br. *walo- 'leader' (see Cadwal).
Cadan	Probably a diminutive of names in Cad-.
Cadell	MW. Catell, Catel, Kadell. Probably from L. catellus 'puppy' (see Cenau). hg, bs
Cadfan	MW. Catman, Katuan. Br. *Catumandus 'battle pony'. hg, t, bs
Cadfannan	MW. Catvannan. A dimunitive of Cadfan. yg
Cadfawr	MW. Catmor. Br. Catumāros 'great battle' (W. cad* 'battle', mawr 'great'). MW. Catmor may be for Br. Catumori 'battle-sea' or 'sea battle' (W. môr* 'sea'). hg
Cadlew	MW. Catleu. The elements may be W. cad 'battle' and glew 'warrior, hero'; less probably llew 'lion'. hg, yg
Cadog	OB. Cadoc, B. Kadeg. From Br. Catācos 'battle-like' (W. cad* 'battle'). hg
Cadogan	MW. Catgocaun, W. Cadwgan. Properly Cadogawn or Cadogon from Br. Catuwocānos 'battle glory' (W. cad* 'battle', gogawn 'glory, honour; satisfaction'). hg
Cadwal	MW. Catgual, G. Cathal. Br. Catuwalos 'battle leader' (W. cad* 'battle'). hg
Cadwaladr	MW. Gatgualart (sic.), Katwalaudyr, OB. Catuualart (sic.). Br. Catuwalatros 'battle-leader' (W. cad* 'battle'). hg, t, bs
Cadwallon	MW. Catgollaun, Catguallaun, Katwallaun, OB. Catuuallon. Br. Catuwallānos 'battle leader' (W. cad* 'battle'). hg, t, bs
Cadwr	MW. Catgur, OB. Catuur. Br. Catuwiros 'warrior, battle hero' (W. cad* 'battle', gŵr 'man'). hg
Cadwystl*	(f.) OC. Catguistl. Br. *Catugēstlā 'battle hostage' (C. kas 'battle', gostel 'hostage'). bm
Caeog	MW. Kayawc. From W. cae 'hedge, fence, enclosure', perhaps meaning 'protector'. yg
Caradog	MW. Caratauc, E. Caratacus, Caractacus. Br. Caratācos 'loving' or 'beloved' (W. caraf* 'I love'). The modern Welsh ought to be *Cardog. hg, t, yg
Carannog	MW. Carannauc. Br. Carantācos 'dear, beloved' (W. carannog). bs*
Cateyrn	MW. Cattegirn. Br. Catutigernos 'battle king' (W. cad* 'battle', teyrn 'king'). hg
Cawrdaf	MW. Caurtam, Caurdaf. Br. Cawrotamos 'most giant' (W. cawr* 'giant'). hg, bgg, t
Cedig	MW. Kedic. Br. Catīcos 'battle-like' (W. cad* 'battle'). bgg, bs
Ceidio	MW. Keidyaw, OB. Cadiou. A hypocoristic of names in Cad-. bgg, yg, t
Cenau	MW. Ceneu, Keneu. From the common noun W. cenau 'whelp, puppy' < Br. *canawū. hg, bgg, yg
Ceredig	MW. Ceretic, Keredic. Identical with Caradog, but with a different ending: Br. *Caratīcos 'loving' or 'loved'. hg, yg, bs
Cian	MW. Gian. Either borrowed from I. Cían meaning 'ancient, enduring' or a late (post-Brythonic) diminutive of W. ci 'dog'. yg
Cilydd	MW. Kilyd. From the W. common noun cilydd 'fellow, companion'. yg
Clodri	MW. Clotri. Br. Clutorīgam (acc.) 'famous king' (W. clod* 'praise, fame, renown; famous', rhi 'king'). hg
Clydno	MW. Clydno. From Br. Clutognāwjos 'knowing fame' (W. clod* 'praise, fame, renown'). bgg, yg, bs
Clydog	MW. Clitauc, Clytauc, C. Klesek. From Br. Clutācos 'famous; famed one' (W. clod* 'praise, fame, renown'). hg, jc
Clydwyn	MW. Clytwin. Br. Clutowindos 'blessed fame' (W. (W. clod* 'praise, fame, renown', gwyn 'white, blessed'). jc
Clynog	MW. Clinog, Clinoch. The origins of this name are uncertain. W. clynnog occurs as a syncopated form of celynnog '(place) abounding with holly' in the place name Clynnog Fawr (Caernarfonshire). It is possible the personal name is the same word with the sense 'holy-like', in the vein of other names derived from trees. However, the records of this name are rather early for such syncope to have taken place and we might expect double -nn- to appear in the Middle Welsh spelling. There are no other clear candidates for the first element of the name. It is possible that this is merely a scribal error: the name only occurs in the Harleian Genealogy and the equivalent people are called Clydno and Kedic in the Bonedd Gwŷr y Gogledd. hg
Coel	MW. Coil, Coyl, Gyl, Coel. From the common noun W. coel 'belief; omen; reputation' < PC. kailā (OI. cél* 'omen, portent'). hg, bgg
Corun	MW. Corun. From L. corōna 'crown, wreath' (W. coron 'crown', corun 'crown (of head), tonsure'). bs
Cunedda	MW. Cuneda, Kuneda. A well-known name, probably from Br. Cunodagos 'good hound' (W. ci 'dog', da 'good'). The modern Welsh form ought to be Cyndda, but it has retained a much older spelling due to it being passed down through written records. hg, bs
Cyfwlch	MW. Chyvwlch. The same as the adjective W. cyfwlch 'complete, perfect, excellent'. yg
Cynan	MW. Cinan, Chynan. Br. Cunagnos 'little hound' (W. ci 'dog', -an* diminutive suffix). hg, bgg, yg
Cyndeyrn	MW. Kyndeyrn, E. Kentigern. Br. Cunotigernos 'hound king' (W. ci 'dog', teyrn* 'king'). This cannot be from Br. Cintutigernos 'first king', as is often stated, since this would produce W. Cynteyrn. t, bs
Cynfan	MW. Chynvan. Br. *Cunomandus 'hound pony' (W. ci 'dog'). yg
Cynfarch	MW. Cinmarc, Kynuarch. Br. Cunomarcos 'hound horse' (W. ci 'dog', march 'horse'). hg, bgg, t
Cynfelyn	MW. Cinbelim, Cinbelin, Chynuelyn, Kynuelyn. Br. *Cunobelinos 'hound of the god Belenos'. hg, bgg, t, bs, yg
Cynfynog*	OC. Conmonoc. Br. Cunomonācos 'noble hound' (C. ki 'dog', W. mynog* 'noble'). bm
Cyngar	MW. Cincar, Kyngar, C. Kengar. Probably Br. Cunocaros 'hound love' (W. ci 'dog', caraf* 'I love'). hg, bs
Cyngen	MW. Cincen. Probably Br. Cunocennos 'hound skin' (W. ci 'dog', cen* 'skin'). hg
Cynin	MW. Cinnin. Br. *Cunignos 'little hound' (W. ci 'dog'). hg
Cynlas	MW. Cinglas. Br. Cunoglassos 'grey hound' (W. ci 'dog', glas* 'blue, green, grey'). hg
Cynri	MW. Kynri. Br. Cunorīgam (acc.) 'hound king' (W. ci 'dog', rhi* 'king'). yg
Cynwal	MW. Gynwal. Br. *Cunowalos 'hound leader'. yg
Cynwr*	OC. Cingur. Br. Cunowiros 'hound man' (C. ki 'dog', gour* 'husband'). bm
Cynwyd	MW. Cinuit, Kynnuyt. Identical in origin to the river name Kent from Br. *Cunētjū, perhaps meaning 'health-giving'. hg, bgg, t
Cynyr	MW. Gynyr. From the nominative of the same name which gives Cynri, Br. Cunorīx 'hound king' (W. ci 'dog', rhi* 'king'). bs
Deigion	MW. Decion. Probably from L. Deciānus < Decius. hg
Deiniol	MW. Deinyoel, E. Daniel. From L. Daniēl. bs
Dewi	MW. Dewi. From L. Davīd. bs
Dinogad, Dingad	MW. Dinacat, Dingat, Dinogat. Br. Dīnocatus 'battle fort' (W. din* 'fort', cad 'battle'). The modern Welsh ought to be *Dingad. hg, jc, yg, bs
Dogfael	MW. Docuael. bs
Dunod	MW. Dunaut, Dunawd. L. Dōnātus. hg, bgg, t, bs
Dwywai	(f.) MW. Dewei. Probably a derivative of Br. dēwā 'goddess' (W. duw* 'god'). bs, yg
Dyfnwal	MW. Dumnagual, Dyuynwal, Dyvynwal, Dyfynwal, B. Dunvel? G. Dòmhnall, E. Donald, Dunmail. From Br. Dumnowalos 'world leader' (W. dwfn* 'deep', G. domhan 'universe'). hg, bgg, yg, bs
Dyfnwallon	MW. Dumnguallaun. Br. *Dumnowallānos 'world learer' (W. dwfn 'deep', G. domhan 'universe'). hg
Edern	MW. Edyrn, Ætern, Edern. From L. Æternus 'eternal'. hg, bs
Ednyfed	MW. Iutnimet, Idnyuet, Edynyuet. Br. Jüdonemetos 'noble lord' or 'lord of the sacred place' (Gaul. nemeton* 'sacred grove', OI. neimed 'sanctuary; sacredness, status'. Properly *Idnyfed in modern Welsh. hg, bgg, bs
Eigion	MW. Eiciaun. Presumably from Br. Oceānus < L. Ōceanus* meaning 'ocean' (W. eigion 'ocean'). hg
Eiludd	MW. Eliud, OC. Iliud. Br. Elujüd- 'many lords' (MW. udd* 'lord'). hg, bm
Einion	MW. Eniaun, Enniaun, Einyaun. Probably from L. Anniānus, Aniānus. The name is usually explained as being from W. einion, eingion 'anvil', which is possible, but the origins of that word are uncertain and the MW. -aun suggests Br. -ān- for the name whilst C. anwan* 'anvil' suggests Br. *-an- for the common noun. hg, bs
Eithinyn	MW. Eithinyn. From W. eithin 'gorse, furze, whin'. yg
Elen	(f.) L. Helena < Gk. Ελενη. hg
Eleuther	MW. Eleuther. L. Eleutherius from eleutheria ‘liberty’. hg
Elfodd, Elfoddw	MW. Elbodgu. Br. Elubodwos 'many crows' (Gaul. bodua-,* OI. bodb, badb 'hooded crow'). hg
Elffin	MW. Elfin, Elffin, Elphin, G. Ailpein, Pict. Alpin. A name of uncertain origin, though L. Alpīnus meaning 'Alpine' would fit the Welsh phonetics perfectly. hg, bgg, yg, bs
Eli	MW. Eli. Probably the Biblical name. yg
Eneas	MW. Eneas. Biblical. bs
Erthgi	MW. Erthgi. From Br. Artocī 'bear hound' (W. arth* 'bear', ci 'dog'). yg
Eudaf	MW. Eudaf. Br. *Awitamos 'most friendly'. yg
Fferfarch	MW. Feruarch. Br. *Feromarcos, meaning either 'wild horse' or 'valiant horse' (see below). yg
Fferog	MW. Ferawc. Perhaps Br. Ferācos 'wild one' from L. ferus* 'wild, fierce' (W. lledffer 'half-wild'), or from W. ffêr 'strong, valiant, ferocious; hero' < L. ferōx 'warlike'. yg
Garfonion	MW. Garbaniaun, Garmonyawn. Probably L. Germāniānus, a derivative of *Germanus. hg, bgg
Geraint	MW. Gereint. From L. Gerontius. yg, t
Gloywfedd*	(f.) OC. Gloiumed. Seemingly 'sparkling mead' (W. gloyw 'bright, shining, sparkling', W. medd, C. medh 'mead'). bm
Gloywgen*	(f.) OC. Gloiucen. Probably meaning 'shining skin' (W. gloyw 'bright, shining, sparkling', C. kenn 'skin'). bm
Godebog	MW. Guotepauc, Godebawc. May be a byname rather than a forename, from Br. Wotepācos 'protective' < PC. wotekʷ- 'hiding place, shelter'. hg, yg
Gogawn, Gwgawn	MW. Guocaun, Gwgawn. Br. Wocānos 'glory' (W. gogawn* 'glory, honour; satisfaction'). hg, yg, t
Gorthebyr	MW. Guortepir. Br. Worteporīx, perhaps meaning 'protective king' with the same root as PC. wotekʷ- 'hiding place, shelter'. hg
Gruffudd	MW. Gripiud, OC. Grifiud. Of uncertain origin and meaning. The second element is certainly Br. jüd- 'lord'. The first may be lL. griphus* < grips 'griffin'. hg, bm
Gwaednerth	MW. Waetnerth. Meaning 'blood-strength' (W. gwaed 'blood', nerth 'strength'). yg
Gwallog	MW. Guallauc. Probably from Br. Wellācos from wello-* ‘better’ (W. gwell). hg, t
Gwen	(f.) MW. Gwen. Br. windā 'white' (W. gwen*). yg
Gwendolen	(f.) Properly *Gwenddolen from W. gwen 'white' and dolen 'ring'.
Gwener	(f.) E. Venus. From L. Veneris, the genitive of L. Venus.
Gwenfraith, Gwynfrith	(f.) OC. Guenbrith. Br. Windobriktā 'white-speckled' (C. gwynn* 'white', brith 'streaked, striped'). bm
Gwengen*	(f.) OC. Guencen. Br. Windocennā 'white skin' (C. gwynn* 'white', kenn 'skin'). bm
Gwengenedl*	(f.) OC. Guencenedl. Br. Windocenetlā 'white family' (C. gwynn* 'white', kenedhel 'nation'). The word 'white' is frequently used to mean 'blessed' in the Brythonic languages, so the name probably means something like 'a family blessing'. bm
Gwidion	MW. Guidgen, Guitgen, Gwydyen. From Br. Widugenjos 'tree-born' (W. gwŷdd* 'trees'). The modern name ought to be *Gwyddien but has retained a partly archaic spelling. hg, yg
Gwladus	(f.) MW. Gwladus, E. Gladys. Taken literally, the name is an adjective formed from the common noun W. gwlad 'country', as if it were a female form of Patrick < L. patricius 'patrician'. This doesn't appear to be a satisfactory explanation for most authorities, however.
Gwrfoddw*	OC. Gurbodu. Br. Wirobodwos 'man crow' (C. gour* 'husband', OI. bodb, badb 'hooded crow'). bm
Gwrgant*	OC. Gurcant. From Br. *Wirocantos 'man circle' or 'man host' (C. gour 'husband', W cant 'outer circle, rim; hoop' or W. cant 'troop, host', OI. cét 'troops'). bm
Gwrgi, Gwrgwn*	MW. Gurci, Gurgi, OC. Gurci, Gurcon. From Br. Wirocī 'man-hound'. OC. Gurcon* is from the oblique stem of the same name (Br. Wirocunam (acc.) > W. Gwrgwn). The natural outcome of the nominative would be W. Gwryg, Gwyryg, so the elements must have been reanalysed after the Brythonic period in order to retain the meaning of the name. hg, bm, bgg
Gwrhaearn	MW. Gurhaiernu. Br. Wiro-isarnos 'iron man' (W. gŵr* 'man', haearn 'iron'). hg
Gwrien	MW. Gwryen. Br. Wirogenos 'man-born' (W. gŵr* 'man'). yg
Gwrwared*	OC. Gurguaret. Seems to be Br. Wiroworetos 'saviour' (C. gour* 'husband', W. gwared 'deliverance, salvation, help', gwaredwr 'saviour'). bm
Gwrwst	MW. Gurgust, Gorust, G. Fearghas. Two similar names have probably converged here: PC. Worgustos ‘great force’ or ‘best choice’ gives the rare OI Forggus* whilst PC. Wirogustos ‘man-force’ or ‘man-choice’ gives OI. Fergus* (G. Fearghas). W. Gwrwst may be from either. hg, bgg, bs
Gwrwystl*	OC. Gurguistl. Br. Wirogēstlos 'man hostage' (C. gour* 'husband', gostel 'hostage'). bm
Gwyddgwn	MW. Guitcun. Br. Widucunam (acc.) 'tree hound' (W. gwŷdd* 'trees', ci 'dog'). hg
Gwyddno	MW. ?Guipno (sic.), Guydno. Probably Br. Widognāwos 'knowing trees' or 'tree-born' (W. gwŷdd* 'trees') but Br. Weidognāwos ‘knowing vision’ (W. gwybod* ‘to know’, gŵydd ‘presence’) is possible. hg, bgg
Gwylog	MW. Guilauc. Perhaps meaning 'watchful, vigilant' from W. gŵyl 'feast, holiday; watch, guard, vigil'. Alternatively from W. gŵyl 'modest, tender, kind, generous, glad' (G. fial 'generous, benign'). hg
Gwyn	MW. Gwynn. Br. Windos 'white' (W. gwyn*).
Gwyndeyrn*	OC. Guentigirn. Presumably Br. Windotegernos 'white king' (C. gwynn* 'white', myghtern 'king', W. teyrn 'king'). bm
Gwynllyw*	MW. Guynlleu. Probably Br. Windoluwī 'fair or blessed ruler' (W. gwyn* 'white', llyw 'ruler'). bs
Gwynwiw*	(f.) OC. Guenguiu. Identical to the Middle Welsh adjective gwynwiw 'white and fair', from W. gwyn 'white' and gwiw 'fitting, proper, fair, handsome, good'. bm
Hedrek	Br. Sitrācos 'strong or bold one' (W. hydr* 'brave, bold, strong').
Heiddyn	MW. Heidyn, OC. Hedyn. From Br. sesjo- 'barley' (W. haidd) with the diminutive ending Br. -innos (W. heiddyn 'a grain of barley'). bm, yg
Hoywgi	MW. Hoewgir (sic.). Meaning 'lively dog' (W. hoyw 'alert, agile, lively', ci 'dog'). yg
Hyfaidd	MW. Himeyt. Probably Br. Sumedgos, Subedgos 'very daring' (W. baidd 'daring'). hg
Hywel	MW. Higuel, B. Hoël. From Br. Suwelos 'well seen' in the sense of 'respectable' (W. gwelaf* 'I see'). hg
Iarnwallon, Haearnwallon	OC. Iarnguallon. Br. Isarnowallānos 'iron leader' (C. horn* 'iron'). bm
Iago	W. Iago, C. Jago, E. Jacob, James. From L. Iacobus from Hebrew. bs
Idnerth	MW. Iudnerth, OC. Iudnerth. Br. Jüdonertos 'lord of strength' (MW. udd* 'lord', W. nerth 'strength'). hg
Idris	MW. Iudris. Uncertain. The first element is clearly Br. jüd- 'lord' and the second may be Rhys* (q.v.). The name may therefore mean 'glorious lord' or 'heroic lord'. hg
Idwawl	MW. Iutguaul. From Br. Jüdowālos, probably 'lord of light' (W. gwawl* 'light, brightness, splendour'). W. gwawl also means 'wall, rampart; boundary', so the name may mean 'march lord'. hg
Ieuaf	MW. Iouab. A by-name meaning 'junior' from W. ieuaf 'youngest'. hg
Ieuan, Ioan, Ifan, Iwan	MW. Yeuan, B. Yann, C. Jowan, E. John. From L. Iōhannes from Hebrew. yg
Ieuenol	MW. Iouanaul, E. Juvenal. From L. Iuvenālis meaning 'youthful'. hg
Illtud	B. Iltud. Probably Br. Elutütos 'many people' (B. tud* 'people, folk').
Ithael	MW. Ithael. From Br. Jüdosagelos 'generous lord' (W. udd* 'lord', hael 'generous).
Jennifer	(f.) W. Gwenhwyfar, E. Guinevere. From Br. Windosɛ̄barā 'white spectre' (C. gwynn* 'white', OI. síabair 'spectre, phantom').
Kadlaouen*	OB. Catlouen. Probably 'battle joy' (B. kad 'fighting, combat', laouen 'joy').
Kadored	OB. Catuuoret. Meaning 'battle protection' from B. kad 'fighting, combat' and gwared 'protection'.
Kadvuz	OB. Catbud. Br. Catubüdos 'battle victory' (B. kad* 'fighting, combat', buz 'profit').
Kanevet	OB. Catnimed. From Br. Catunemetos, the first element is B. kad* 'fighting, combat' and the second is neved 'sanctuary'.
Katouarn	OB. Cathoiarn. 'Battle iron' from Br. Catu-isarnos (B. kad* 'fighting, combat', houarn 'iron').
Kenal	From Br. Cunosagelos 'generous hound' (C. ki 'dog', hel* 'generous').
Keneder	Br. Cunositros 'bold hound' (C. ki 'dog', W. hydr* 'bold, brave, strong').
Kenver	Br. Cunomāros 'great hound' (C. ki 'dog', meur* 'great').
Lleënog*	MW. Leennauc. This would seem to be the same as W. llenog 'priestly, literate, learned; scholar, cleric', from W. llên 'literature, learning; clerical' < L. *legenda 'to be read'. bs
Lleuddin*	MW. Leudyn, Leudun. Probably from Br. Lugudīnos 'fort of the God Lugus' (W. Lleu 'Lugus', din 'fort'). Lleuddin is the eponymous founder of Lothian or Lleuddiniawn 'territory of Lleuddin', so the name may actually be that of a place originally. The element din does occur in other personal names, however, and the suffix -iawn, -ion is attached to personal names as in W. Ceredigion 'Cardigan'. bs
Llywarch	MW. Llywarch, OC. Loumarch. Br. Lugumarcos 'horse of the god Lugus' (W. Lleu* 'Lugus', march 'horse'). bm, bgg, yg, t
Llywelyn	From Br. Lugubelinos, a combination of the divine names Lugus* (W. Lleu) and Belenos.
Llywri	MW. Llywri. Probably Br. Lugurīgam (acc.) 'king of the god Lugus' (W. Lleu* 'Lugus', rhi 'king'), but perhaps the first element is W. llyw 'rudder; ruler'.
Macsen, Maxen	MW. Maxim, Maxen, C. Massen. From L. Maximus (in particular the Roman emperor Magnus Maximus, known as Macsen Wledig in Welsh). The name was evidently recorded at an early date according to its Latin origins and the modern Welsh name is a learned, phonetic rendering of the medieval written form. If the name had continued in use it would have become W. *Meisyf. hg, bgg, t
Madien	MW. Madyen. Br. Matugenos 'bear-born' (OI. math* 'bear'). yg
Madog	MW. Madawc. From Br. Matācos, either meaning 'bear-like' (OI. math* 'bear') or 'good' (W. mad 'good, virtuous, beneficial'). yg
Mael	Br. Maglos 'prince' (W. mael* 'prince, chieftain, lord').
Maelgwn	MW. Mailcun, Maelgun. Br. Maglocunam (acc.) 'hound prince' (W. mael* 'prince, chieftain, lord', ci 'dog'). hg, bs
Maelgwyn	Br. Maglowindos 'white prince' or 'blessed prince' (W. gwyn* 'white; blessed', mael 'prince, chieftain, lord'). t
Maelog	OC. Maeloc. Br. Maglācos 'princely' (W. mael* 'prince'). bm
March	OC. March. From the common noun meaning 'horse' (W. march, C. margh). bm, t
Marchell	(f.) MW. Marchell. From L. Marcella < Marcus. jc
Marchlew	MW. Marchlew. Br. Marcolewū 'horse lion' (W. march* 'horse', llew 'lion'). The second element may be W. glew 'bold; hero'. yg
Maredudd	MW. Margetiud, Morgetiud, E. Meredith. Of uncertain origin, the final element is Br. *jüd- 'lord'. hg
Marro	MW. Marro. Of uncertain origin, but perhaps a hypocoristic of a name in March-. yg
Mawn, Maun	MW. Maun. Uncertain, but potentially related to the divine name Mogons meaning 'great', or to the epithets of St Patrick Magonus, Mauonius, Maun, which may be from the same source or from PC. magu- 'servant' (C. mowes* 'girl', MW. meudwy 'hermit'). hg
Meddwystl*	(f.) OC Medguistl. The second element is clearly C. gostel, W. gwystl 'hostage', but the first may be either C. medh, W. medd 'mead' or W. medd 'power, authority'. bm
Meirchion	MW. Merchianum, Meirchaun. From L. Marciānus, a derivative of Martius, Marcius. hg, bgg, t
Meirion	MW. Meriaun, Meiryaun. From L. Mariānus, a derivative or Marius. hg, bs
Merfyn	MW. Mermin, OC. Mermin, E. Mervin, Mervyn, Marvin. A raft of explanations have been given for this name, none of which are particularly satisfactory. The only reliable source available to me gives the curious 'eminent marrow' from W. mêr 'marrow (literal and figurative)' and myn 'eminent', the latter of which does not occur in the Geiriadur Prifysgol Cymru* so is questionable. Other suggestions such as 'sea friend', 'sea lover' and 'sea hill' obviously take the first element to be W. môr 'sea' but have inexplicable second elements. Môr is the only reasonable candidate for the first element and it occurs in several other Brythonic names. The second element is less certain, but W. myn 'desire, wish, will' or myn 'crown, diadem' would both fit. hg, bm
Merin	MW. Merin. Probably Br. Morīnos 'sea-like' or Morignos 'little sea' (W. môr 'sea'). yg
Merwydd	MW. Merguid. Br. Moriwidus 'sea tree' (W. môr* 'sea', gwŷdd 'trees'). hg
Meurig	MW. Mouric. L. Mauricius < Maurus 'dark-skinned, Moorish'. hg
Modred	OC. Medrod, W. Medrawd, E. Mordred. Probably from Br. Mātrātos or the like < Mātr- 'mother'. bm
Môr	MW. Mor, OC. Mor. Simply 'sea' (W. môr 'sea'). hg, bm
Mordaf	MW. Mordaf. Perhaps Br. *Mārotamos meaning 'the greatest'. bgg, t
Morfael	MW. Mormayl. Br. Morimaglos 'sea prince' (W. môr* 'sea', mael 'prince, lord'). hg
Morgan	MW. Morcant, OC. Morcant. Br. Moricantos 'sea circle' (W. môr* 'sea', cant 'outer circle, rim; hoop') or 'sea host' (W. cant 'troop, host', OI. cét 'troops'). hg, bm, t
Morial	MW. Moryal. Br. Morigalos 'power of the sea' (W. môr* 'sea', gallaf 'I am able'). yg
Morien	MW. Morgen, Moryen. Br. Morigenos 'sea-born' (W. môr* 'sea'). hg, yg
Morudd	MW. Moriud. Br. Morijüd- 'sea lord' (W. môr* 'sea', udd 'lord'). hg
Mynog	MW. Mynawc. Br. Monācos 'noble' (W. mynog* 'noble, eminent; lord'). yg
Myrddin	B. Merzin, E. Merlin. Br. Moridīnon 'sea fort' (W. môr* 'sea', din 'fort'). The original name for Carmarthen (W. Caerfyrddin), but possibly also a personal name since both elements are known in other Brythonic names.
Neithon	MW. Neithon, Nwython, Pictish Nechtan, G. Neachdainn. Of unknown origin, but perhaps originally a divine name like Br. Nektonos, related to L. Neptūnus* 'Neptune'. hg, yg
Nudd	MW. Nud. From the divine name Br. *Nüdens. bgg, t, bs
Nyfed	MW. Nyuet. From the common noun Br. nemeton 'sacred place' or the adjective nemetos 'noble'. yg
Owain	MW. Ywein, Ewein, Eugein, Ouen, Owein, B. Ewen, E. Owen, Ewan, G. Eòghann. Either from PC. Esugenjos 'born of the god Esus*' or Gk. Ευγενιος (Eugenios) 'well born'. hg, yg, t, bs
Padarn	MW. Patern. From L. Paternus 'paternal'. hg
Pasgen	MW. Pascent. Of uncertain origin, probably derived from L. Pascha 'Easter' (W. Pasg) or L. pāscō 'I feed, foster, keep, cherish; graze' (W. pasg 'fattened, pasgaf 'I feed, fatten, nourish'). The present participle L. pascentem (acc.) 'feeding, nourishing, cultivating' may be the direct origin of the name, perhaps with Christian overtones of spiritual nourishment. hg
Pedr	MW. Petr, Pedyr, E. Peter. From L. Petrus < Gk. Πέτρος (Petros) meaning 'stone, rock'. hg, bs
Peithan	MW. Peithan. From Br. *pekto- 'strength'.
Peredur	MW. Peretur, Pheredur, Peredur. no serious attempts seem to have been made to explain this name; it may contain the L. suffix –tōrius. hg, bgg, yg, t
Rhiainfellt	(f.) A compound of W. rhiain 'maiden' (originally 'queen' from the same root as W. rhi 'king') and mellt 'lightning'.
Rhian	(f.) An alteration of W. rhiain 'maiden'.
Rhiannon	(f.) From Br. Rīgantonā 'divine queen' (W. rhiain* 'maiden').
Rhiol*	OC. Riol. Probably Br. Rīgālos 'kingly' (C. riel* 'royal', W. rhi 'king'). bm
Rhiwallon	MW. Rhiwallawn. Br. Rīgowallānos 'king leader' (W. rhi* 'king'). t
Rhodri	MW. Rotri. Perhaps Br. Rātorīgam (acc.) 'king of troops' (W. rhawd* 'course; troop', rhi 'king') or Rotorīgam (acc.) 'wheel king' (W. rhod* 'wheel'). hg
Rhufawn	MW. Rumaun, Ruvawn. L. Rōmānus meaning 'Roman'. hg, yg, t
Rhun	MW. Run. Perhaps PC. roino- 'hill, plain' (G. raon* 'plain, field'). hg, t, bs
Rhydderch	MW. Riderch, Ryderch. Often said to mean 'very red' or 'reddish-brown' in connection with OI. derg 'red' (G. dearg), but the root which gives OI. derg would yield dery in Welsh. The origin is in Br. Roderkos, connected with OI. derc 'eye', dercaim 'I behold', Gaul. derco- 'eye', so the name means 'well-seen, remarkable' or something similar. hg, bgg, t
Rhys	MW. Rys. Related to W. rhyswr 'hero, champion, warrior' and rhysfa 'attack, assault, combat'. yg
Riwal	Br. Rīgowalos 'king leader' (B. ri 'king').
Sawyl	MW. Samuil, Sawyl. From L. Samuēl from Hebrew. hg, bgg, bs
Seisyll, Seisyllt	MW. Seissil. From L. Saxillus < Saxō* 'Saxon'. hg
Selyf	MW. Selim, E. Solomon. From L. Salomō from Hebrew. hg
Serwan	MW. Serguan, Seruan, E. Serf, Servan. From L. Servanus < servus 'servant'. hg, bgg, t
Serwil	MW. Serguil. L. Servīlius < Servius. hg
Siân	(f.) E. Jane. Borrowed from OF. Jehanne via Middle English.
Tanghwystl, Tangwystl	(f.) MW. Tancoystl, OC. Tanguistl Br. *Tancogēstlā 'peace hostage' (W. tanc 'peace, truce', gwystl 'hostage'). hg, bm
Taliessin	MW. Talyessin. Br. Talojastīnos 'radiant brow' (W. tâl* 'end, forehead', iesin 'fair, beautiful; radiant, shimmering, bright'). yg, t
Tegid	MW. Tacit. From L. Tacitus 'unsaid'. hg
Teilio	MW. Teilyau. A hypocoristic (pet name) of *Eiludd with the pronoun ty 'your' prefixed. bs
Tewdrig	MW. Tewdric. A borrowing from OE. Þeodric.
Tewdwr	MW. Teudebur, W. Tewdwfr, E. Tudor, Theodore. An attempt to render L. Theodorus < Gk. Θεοδωρος using Welsh elements. The name would literally mean 'fat water'. hg
Tudfwlch	MW. Tutuwlch. A compound of W. tud 'people, tribe, nation, family' and bwlch 'cleft, mountain pass', the symbolism of which is not entirely clear. bgg, yg
Tudwal	MW. Tudgual, Tutagual, Tutwal. Br. Tütowalos 'people leader' (W. tud* 'people, tribe, nation, family'). hg, bgg, t
Twrch	MW. Twrch. From the common noun W. twrch 'boar'. yg
Unwst	OC. Ungust, G. Aonghas, E. Angus. From PC. *Oinogustus 'one force'. bm
Urien	MW. Urbgen, Yrien, Uryen. Probably from Br. Orbjogenos 'heir born' (OI. orbae* 'legacy, inheritance' < PC. orbjo-), which regularly yields MW. Yrien. The origin of the U- has been ascribed to rounding caused by the original -b-, or to a lengthening of the initial O- > *Ō- > U-. Alternatively, U- may have begun as an attempt to write the rounded front vowel created by i-affection of o, with some scribes retaining this spelling even after the pronunciation had merged with Y-. hg, bgg, t, bs
Yannig	A diminutive of B. Yann 'John'.
Yezekael	OC. Iudicael, E. Judicael. Probably Br. Jüdicosagelos 'generous lord'. The Br. stem jüd- may derive from L. iūdex 'judge'; if so, this name appears to preserve the original consonant stem of a Br. jüdicam (acc.), whereas other names with jüd- appear to show that it was reanalysed as a vowel stem such as *jüdos.

Notes

The Br. *jüd- may derive from L. iūdex 'judge' or it may be native PC. *joud-. As a common noun it appeared in Middle Welsh as udd 'lord' and it became a common element in personal names.