Dunn (surname)  The surname Dunn has several different origins. In some cases it is an Anglicised form of the Irish surname "Ó Duinn", meaning "grandson of "Donn""; the Gaelic "Donn" was originally a byname, meaning "brown-haired" or "chieftain". Another origin of the surname "Dunn" is from the Middle English "dunn", meaning "dark-coloured"; this name originated as a nickname for one with dark hair or skin. Another origin is from a habitative name, derived from Dun in Angus, Scotland; this place name is derived from the Scottish Gaelic "dùn", meaning "fort". Another origin is from the Gaelic "donn", meaning "brown".