Strictly a wild guess, but I'd say the short wire is the ground since there'd probably be a lot of things nearby to connect it to wherever it gets mounted in the aircraft, and the fact that the terminal end has the teeth, which would cut through paint and primer to establish a good connection to the structure when attached to a ground stud. No need for that on the hot wire that is being connected to other wiring instead of terminating at the structure.

Don't trust me though...