Dallas is a surname of Scottish and English origin, as well as a given name.
When of Scottish origin the name is a habitational name, derived from Dallas near Forres.
This place-name is likely derived from the British dol "meadow" + gwas "dwelling" (compare Gaelic dail + fas).
This name also appears in County Londonderry, Northern Ireland.
[1] The surname, when of Scottish origin, is considered by some to be a sept of Clan Mackintosh.