The mountain's name, Sliabh Cuilinn, is read as Culann's mountain, after the metalsmith Culann. Tradition says the hero Cú Chulainn spent his childhood, as Sétanta, here, and that this is where he earned his adult name.
In the story Culann invites Conchobar mac Nessa, king of Ulster, to a feast at his house on the slopes. On the way Conchobar stops to watch boys playing hurling and is so impressed by Sétanta that he asks him to come along. Sétanta says he will follow when his game is done. Conchobar forgets him, and Culann lets his fierce hound loose to guard the house. When Sétanta arrives the hound attacks and he kills it, in one version by hurling it against a standing stone, in another by driving his hurling ball down its throat.
Culann is heartbroken. The boy promises to rear him a replacement and in the meantime to guard his house himself. The druid Cathbad then declares that from that day he will be called Cú Chulainn, Culann's Hound. The nearby Gap of the North is where, in the Táin, he is said to hold off Queen Medb's army single-handed.
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