I was looking for somewhere in my old station wagon to get 12v DC (besides the lighter, I am using that for another thing) to attach something to, and I found in the back left floor panel of the trunk a connector with green/purple and black wires. I thought it might be 12v for something, but testing it with the car one showed nothing.

What could it be for? Is there somewhere that I can get 12v safely?

Thanks