Gordon is a traditional Scottish clan name (see Clan Gordon) and it is now a common given name and a less common surname. It is thought to be Celtic for "great hill" from the Celtic words "gor" which means "great" and "dun" which means "hill".
It is also a fairly common surname of some Eastern European Jews (Hebrew: גורדון Russian: Гордон); its origin in this usage means "a person or pedigree from Grodno". Variations are Gordin, Gordan, Grodner, etc.