Douglas, occasionally spelt Douglass, is a Scottish surname.
It is thought to derive from the Scottish Gaelic dubh glas, meaning "black stream".
There are numerous places in Scotland from which the surname is derived.
Douglas is a habitational name, which could be derived from any of the many places so-named.
[3] According to George Fraser Black, in southern Argyllshire the surname is an Anglicised form of the surnames MacLucas, MacLugash (which are derived from the Gaelic Mac Lùcais).