Duncan (surname)
Duncan is a Scottish surname. The Scottish Gaelic name Donncheann or Donnchadh are bynames composed of the elements donn, meaning "brown" or "dark" from Donn a Gaelic God; and chadh, meaning "chief" or "noble". In some cases when the surname was used in County Sligo, Ireland, it is an Anglicized form of the Irish Gaelic name MacDonough or Mac Donnchadha and Ó Duinnchinn, meaning "descendant of Donncheann". The surname Duncan is represented in Scottish Gaelic as MacDhonn.