Donahue is the Americanized version of Irish surname Donohoe, which, in turn, is an Anglicized version of the ancient Irish name “Donnchadh” (sometimes “Donncha”).

Donncha was a common “first name” in 9th Century Ireland, and when the use of surnames became more common in Ireland around the 10th Century, many people looked to a respected common ancestor to form a surname. The ancestors of the modern Donahues took the name O’Donnchadha, meaning “the son of Donnacha” or “of the line of Donnacha”. The modern Donahues are descended from one of at least eight unrelated Donnachas, each of whose descendants adopted the surname O’Donnchadha.