 This appears to be based on the false assumption that his father was the eponymous ancestor of the Dál nAraidi sept of Uí Chóelbad.Other unreliable and late sources may have linked Mac Cairthinn with the Uí Néill, by making his father Cóelbad a son of Niall.According to Dáibhí Ó Cróinín the above demonstrates "how far north Leinster's territorial claims once extended" and that warfare between the Laigin and the emerging Uí Néill occurred in the north of Brega and on the plains of what is now County Meath and County Westmeath.