A male given name from Scottish Gaelic anglicized from Scottish Gaelic Donnchadh; the name of two early saints and of two kings of Scotland. • A Scottish surname originating as a patronymic. • A surname from Irish, a variant of Dinkin. • An Irish surname, a variant of Donegan. • An Irish surname, a variant of Dunican. • An Irish surname, adopted as an anglicization of Ó Donnchadha (whence Donoghue). • A locality in Kangaroo Island council area, South Australia; named for politician John Duncan. • A city in the Regional District of Cowichan Valley, British Columbia, Canada; named for early settler William Chalmers Duncan. • A locale in the United States: • A town in Greenlee County, Arizona; named for copper businessman Duncan Smith. • A township in Mercer County, Illinois. • A census-designated place in Hancock County, Iowa. • An unincorporated community in Casey County, Kentucky. • An unincorporated community in Mercer County, Kentucky. • A township in Houghton County, Michigan. • A town in Bolivar County, Mississippi. • A township in Sullivan County, Missouri. • An unincorporated community in Webster County and Wright County, Missouri. • A village in Platte County, Nebraska; named for early resident Wood B. Duncan. • An unincorporated community in Buckhorn Township, Harnett County, North Carolina. • A city, the county seat of Stephens County, Oklahoma; named for early settler William Duncan. • A township in Tioga County, Pennsylvania. • A town in Spartanburg County, South Carolina; named for landowner Leroy Duncan. • A river in British Columbia, Canada; running 206 km near Mount Dawson into the Kootenay Lake; named for prospector John Duncan. • A short river in the Southern Alps, West Coast Region, New Zealand.