The Celtic heroic saga in the British islands may be divided into the two principal groups of Gaelic (Irish) and Brython (Welsh), the first, excluding the purely mythological, into the Ultonian (connected with Ulster) and the Ossianic. The Ultonianis grouped round the names of King Conchobar and the heroCuchulainn, " the Irish Achilles," the defender of Ulster against all Ireland, regarded by some as a solar hero.
On the west of the northern part of the English kingdom of Bernicia, severed from that by the Forest of Ettrick, and perhaps by the mysterious work of which traces remain in the " Catrail," was the Brython or Welsh kingdom of Strathclyde, which then included the territory and population, later anglicized, of Renfrewshire, Ayrshire, Lanarkshire, Dumfriesshire, and, south of the historic border, Cumberland and Westmoreland to the Derwent.
(3) pp, tt, cc became respectively ph or ff, th, ch; thus peccatum gave pechawd, later pechod; and Brittones gave Brython.
(See Celt, sec. Celtic Literature.) Of Brython origin is the cycle of King Arthur (Artus), the adopted national hero of the mixed nationalities of whom the " English " people was composed.