[see also Hiberno-Brittonic catu-tegernos, battle-lord].
A legendary ancestral king of Leinstermen, thought to have reigned just before Conn Cétchathach [of the Hundred Battles]. In the most common version of the story, Conn kills Cathaír and displaces him; in variants Goll mac Morna or others do the killing. In Esnada Tige Buchet [The Melodies of Buchet's House], Cathaír's daughter Eithne Tháebfhota is fostered to Buchet, while his twelve uncontrollable sons eat all Buchet's provisions; later Eithne marries Cormac mac Airt and bears his son, Cairbre Lifechair. His son Failge is the eponym of Co. Offaly in Leinster. Another daughter was Cochrann, the mother of Diarmait Ua Duibne. Fionn mac Cumhaill is often reckoned to have been born in his reign. The name is often translated as ‘Charles’, with which it has no etymological link. See the poem of James Clarence Mangan, ‘The Testament of Cathaeir Mor’ (1847).