It's an expression derived from Jesus (Jeepers) Christ (Creepers), one of numerous mild epithets created to avoid taking the name of the lord in vain. In 1938 it was the title of a song. (Jeepers...
The Creeper in Jeepers Creepers eats people because he takes in to himself the part that he eats to replace that own bodypart in himself. Example, if he needs new eyes he would eat someone's eyes.