''TheTá ainm na namebhFear ''Fir Domnann'' isbunaithe basedar on thean rootbhfréamh ''dumno''-, whichdomhan. meansbothFeictear ‘deep’go andminic ‘thean world’.iarmhír The suffix -''-on''-oftenmar occurschuid ind'ainmneacha Gaulishdiaga andGallaigh Britishagus divine namesBriotanaigh. ThetribalIs nameléir [[Dumnonii]],mar foundsin ingo Britain,gciallaíonn ainm wouldna thereforetreibhe meansa ‘peopleBhreatain, ofna the[[Dumnonii]], god of the world’. Old Irish ''‘muintir/fir''meansdhia ‘men’, and soan domhain''Fir. Domnann''hadDe thebharr samechosúlacht meaningna as the British tribal namen-ainmneacha, leadingmoladh togo conjectureraibh that these tribes had a commonchomh-bhunús originacu.<ref>J.T. Koch, ''Celtic Culture: a historical encyclopedia'' (2006), lch. 750.</ref> ForexampleThug Ó Raghallaigh le fios, mar shampla, ina [[O'Rahilly'ssamhail historicalstairiúil Uí Raghallaigh|shamhail modelstairiúil]] proposedgur that the Domnann were adhream [[P-CelticCeilteach]],preréamh-GoidelicGaelach peopleab who,ea alongiad witha therinne [[Galeóin]],ionradh invadedar theóir south-eastdheisceart coastna ofhÉireann Irelandi fromd Britaindteannta leis na [[Galeóin]].<ref>T. F. O'Rahilly, ''Early Irish History and Mythology'' (Institiúid Ard-Léinn Bhaile Átha Cliath, 1946)</ref> O’Rahilly’stheoryNó ofghlactar P-Celticgo precedingforleathan [[Goidelic]]leis inan Irelandsmaoineamh isseo not widely accepted by experts todayinniu, butach theis ideaamhlaidh ofina someainneoin connectionsin betweengo the British and Irishbhfuil tribesnasc oféigin theidir samean namedá remainstreibh.<ref>J.T. Koch, ''Celtic Culture: a historical encyclopedia'' (2006), lch. 750.</ref>