Dunn is a surname of English and Scottish origins.
It has several different origins.
Typically the 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.
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".