"Can someone please tell me what this could be used for or was intended to be used for."
We can probably come up with a hundred and one things it could be used for, but the original purchaser is the only one who can tell you what it WAS intended for.
I've heard of people doing dishes with the outside shower, perhaps some thing used during that? Again radio/tv, phone charger.
I'm going with 12v hairdryer to be used after the outdoor shower?