If I'm honest, it doesn't look stock from what I can tell in the pic. My guess is that someone installed it aftermarket, or self done most likely. I also think i spy what looks like a fuse holder near the battery.
My guess is that it is a dedicated electrical run, for something like lights, a horn, etc. With that guess in place, my money is on it going to the firewall, or at least it did.
I would check lights and everything to make sure everything is working. I also agree that more closer pics would be a great help.