CONALL CERNACH . The father of Conall Cernach was Amhairghin, the famous poet and hero of the Ulstermen, and he himself is represented as the most important of the Ulster heroes save Cú Chulainn. He is also sometimes named as a foster brother of Cú Chulainn, though evidently more mature in years: at the time of Cú Chulainn's birth he was already one of the Ulster warriors, and it was he who guarded the southern border of Ulster when the youthful Cú Chulainn came there to perform his first initiatory exploit in the epic Táin Bó Cuailnge (The cattle raid of Cuailnge). But whereas Cú Chulainn died without progeny, Conall Cernach appears in the genealogies as the ancestor of the Cruthin or Pictish tribes of Ireland. In Fledh Bhricrenn (The feast of Bricriu) he contests the prize of the "champion's portion" with Cú Chulainn but has to give best to the younger hero. It was Conall Cernach who avenged Cú Chulainn's death, beheading his slayer Lughaidh mac Con Roí. When he himself was slain and beheaded by his lifelong foes the Connachtmen, it is said that his head was so large that it could have held four men playing "chess" (fidhchell) or a couple lying together.
He is sometimes described as cloen ("crooked") because his inveterate enemy, the Connachtman Cet mac Mághach, to whom he was a nephew, had stamped his heel upon his neck after his birth, for it was prophesied that he would kill half the men of Connacht. The name Conall derives from a Celtic form, *cuno-valos ("strong as a wolf"), and, appropriately, his epithet cernach may mean "triumphant" and is so understood in early texts. But there was also an alternative interpretation. According to the Cóir Anmann (Fitness of names), the word cern means "bump, protuberance" as well as "victory," and Conall's epithet is said to refer to the fact that he had "a lump on one side of his head as big as the boss of a shield." Because of this and an episode in the tale of The Cattle Raid of Fróech, Anne Ross has suggested that there is an affinity between Conall Cernach and the Gaulish horned god Cernunnos (Pagan Celtic Britain, London, 1967, pp. 149ff.). Though she does not advert to it, her argument is supported by the fact that Irish cern is etymologically related to Irish corn, Latin cornū, Old High German horn, and so on.
Further information on Conall Cernach can be found in Rudolf Thurneysen's Die irische Helden- und Königsage bis zum siebzehnten Jahrhundert, 2 vols. (Halle, 1921), the classic study of Táin Bó Cuailnge.
Proinsias Mac Cana (1987 and 2005)