From Middle English dun, dunne, from Old English dunn ("dun, dingy brown, bark-colored, brownish black"), from Proto-Germanic *dusnaz ("brown, yellow"), from Proto-Indo-European *dʰewh₂- ("to smoke, raise dust"). Cognate with Old Saxon dun ("brown, dark"), Old High German tusin ("ash-gray, dull brown, pale yellow, dark"), Old Norse dunna ("female mallard; duck").
Alternative etymology derives the Old English word from (compare Middle Welsh dwnn), from Proto-Celtic *dusnos (compare Old Irish donn), from Proto-Indo-European *dʰews- (compare Old Saxon dosan). More at dusk.
Unknown; perhaps a variant of din. Several sources suggest origin from Joe Dun, the name of a bailiff known for arresting debtors, but this is controversial.
Uncertain; likely from the color.
From Irish dún or Scottish Gaelic dùn, from Proto-Celtic *dūnom. Cognate with Welsh dinas. town.