Muireadhach mac Aedh

Muireadhach mac Aedh, Lord of Clann Cosgraigh, died 1124. He was a distant cousin of the Muintir Murchada, of whom the O'Flahertys were chiefs.
The Annals of the Four Masters, "sub anno" 1124, state that "Muireadhach (i.e., lord of Clann-Cosgraigh), the son of Aedh, son of Ruaidhri, died an ecclesiastic." John O'Donovan, who edited the 1856 publishing of the Annals of the Four Masters, inserts "O'Flaithbheartaigh" after Ruaidhri's name, but this appears to be a mistake; O'Donovan confuses the Lord of Clann Cosgraigh with another Muireadhach mac Aedh mac Ruaidhri, who was an actual O'Flaherty. The McHughs, according to O'Flaherty, descend from Dungalaigh m. Cenn Faelad m. Colgan in generation 12 of his genealogical table, whereas the Muireadhach m. Aedh m. Ruaidri O'Flaherty is in generation 111 in the lineage of the O'Flahertys, as cited in O'Hart.
Muireadhach's immediate descendants adopted the surname Mac Aedha. The surname is now rendered McHugh or Hughes, less commonly McGagh (better reflecting the Irish pronunciation).
Genealogy.
From Leabhar na nGenealach, 201.6, pp. 442–43, volume I.