what is this plug for? wiring under battery apron

1990 LX convertible. I am looking at the harness that comes through the large hole int eh battery apron. 2 separate bunches of conductors come through, and one plugs into the washer resevoir. The other, the one in question... The infamous mystery plug... has a rubber block off protecting the end and has 8 pins, but only 7 conductors leading into it. It is fastened to the undersiide of the battery apron, by the horns, and the washer fluid resevior. Any clue as to it's function? Just curious as I am not sure I entirely understand the point of it. It seems like a lot of wires with no point. The fact that it has a rubber block off plug in teh end tells me that ford never bothered to plug anything into it at the factory, yet, I am sure someone's car has this plug put to a good use.


Any idears?
 
I wonder if its the driving light plug. Is there another one just like it on the passinger side? kinda oval in shape?