After Culan had crafted weapons of transcendent excellence for Conchobar on the Isle of Man, he accepted the offer of the ambitious young man from #Ulster, to dwell in his realm, and settled on the plain of Murthemne, which was fabled to have been formerly situated beneath the sea. It was here that he was visited by Conchobar, accompanied by his Court and Setanta. Culann was the possessor of a terrible hound, which was slain by the youthful Setanta; who was in consequence called #CúChulainn, i.e., Culann's hound.`
Source: https://www.sacred-texts.com/neu/celt/fim/fim04.htm#Celtic