It's hard to tell from the picture, but it looks like there is a quick disconnect as part of offending wire. If not you can give yourself a couple inches on said wire from the door tap in order to be able to reconnect it in the future and cut it. seal the open wire with some electrical tape.
Jeeps have a much higher chance of unidentifiable previous owner mods.. I have something behind my glove box that can be plugged into the cigarette lighter port... no idea what it does. Accept that you may never figure out what it is.
