What kind and size of wire do you have? If it's reasonably heavy stranded wire, maybe 12 gauge or so, it's a 12V DC circuit and probably a switch for a light (but it could be a location for a 12V lighter receptacle). If it's 12 or 14 gauge solid wire from Romex cable, it would probably be for a 120V outlet, and there should also be a ground wire.
On my '98 Coachmen motorhome, they consistently use white wire for 12V ground leads and various colors of wire for the positive leads, the colors generally being sorted out by circuit. If you find the corresponding color of wire at the 12V fuse panel you could perhaps find out what sort of label it has for the fuse, which may or may not be helpful.
