McMahon surname meaning

McMahon is an Irish Anglicization of Gaelic Mac Mathghamhna, “son of Mathghamhain”—the same “good calf”/“bear” byname behind Mahoney. Two historically unrelated chieftain families bore the name in Clare (Thomond) and Monaghan (Oriel). MacMahon, Mac Mahon, and Mahon are common variants in Irish and American records. In northern Ireland Matthews sometimes translated the surname because Matha was an Irish form of the Biblical Matthew. Parent’s name is high confidence: McMahon is a straightforward Mac-patronymic from a personal byname shared with the Ó Mathghamhna (Mahoney) tradition.