What does this button do???????

I have a switch in my car wwwwwwwway down by the brake pedal, but on the edge of that same plastic panel. I haven't gotten around to following wires though, but no matter which position it's in, noting changes. I can only assume (due to it's remote *** location) it'd be a kill switch. There used to be an MSD (or similar) box in the car too, so possibly it was a kill switch linked to that.
It's not factory, to reassure you


