Source : Webster's Revised Unabridged Dictionary (1913)

Auto- \Au"to-\
   An abbrev. of automobile, used as a prefix with the meaning
   of self-moving, self-propelling; as, an autocar, an
   autocarriage, an autotruck, etc., an automobile car,
   carriage, truck, etc.

Auto- \Au"to-\ [Gr. ? self.]
   A combining form, with the meaning of self, one's self, one's
   own, itself, its own.