[Ir., of the (wine-)red hand].
A king of Connacht (d. 1224), thought to be the brother or son of the last high king of Ireland, Ruaidrí Ua Conchobair [Rory O'Connor]. Many legends have attached themselves to Cathal. After his conception out of wedlock, his father's legal wife and queen tried unsuccessfully to thwart his birth. He was spirited away to a distant area, but he could always be identified by a winered birthmark on his hand, which he covered with a glove. When a passing stranger told him that the throne of Connacht was vacant, Cathal ceased his hard farm labour, cutting rye, and went to assume his throne by showing his birthmark.
See James Clarence Mangan's poem ‘A Vision of Connaught in the Thirteenth Century’ (c.1845).