Mystery wire in headlight harness

So a bachelor's "nagging wife" telling him to slow down. Were those available in 1969 (the "fuel pacer," not the nagging wife)?

I am looking to move that wire (I am relocating the horn wire to the headlight harness since that makes more sense than the engine harness). Is it a key on wire (talking out loud, dont expect anyone to know)? I need one to feed the reverse lights switch (it should be in the wiper harness, but it is not, and I didnt find it anywhere else). If it is, I can use that one.

Time to research!