Random plug found at rear bumper

[MEMO43]

So one thing led to another
What should have been a quick break job for new shoes an possible re surface of the drums.
I ended up replacing the rear shoes an drums, since I was there I replaced all the springs.
Then ended up with new cylinders since both had torn rubber ends. The rear passenger showed signs of leakage (glad it wasn't the axle seal)

But after buttoning everything back together I noticed this beauty
Rig is a stock 83 k5 blazer
Simberado package, with the custom lake tahoe rust.
Colors purple. Yellow, green an blue
I know my rear tailgate doesn't work even though I have voltage at the switch an had the motor rebuild.
Thanks in advance

 

[Bent77]

Tail lights, plug that hummer in and you should be good

Mine likes to spit itself out, I put a few wraps of electrical tape on it

 

[MEMO43]

Thanks bent for the reply
Just didn't want to plug something without knowing what it is actually for.

 

[SpeedlabDan]

Also where the camper special harness plugs in between. I had the same question when i found a 6 foot lead back there.