The story
* As a Scottish Gaelic and Irish surname, from Donnchadh, a name composed of donn (“brown”) + cath (“battle”). Also spelled as Donagh and Donaghue, Donahue. * Also as an Irish surname, Anglicized from Ó Duinnchinn, from donn (“brown”) + ceann (“head”).
Etymology from Wiktionary, CC BY-SA 4.0.