It was probably based on this 1973 movie:
but it's totally amazing the drawing of the StarWars character is actually an endoskeleton under flesh... The robot from the "West World" movie wasn't, it was just chips and stuff but not actually a metal cranium like Stan Winston's.
But Cameron allegedly took from many sources, one was a particular episode of "The Outher Limits" I think. Though he declared he totally DREAMED the whole movie.
Fucking dirty liar.