What does this switch activate?

See if your reverse light switch is unhooked.

Here's what this is starting to look like..........

Someone "may have used" the factory backup light wiring to activate a nitrous switch.

That 2 terminal connector you are holding looks like the backup switch connector, and the wire colors match.

Either that or it was "wired to something" and coincidence that your backup lamp connector just happened to be "hanging" there.