why is the bathroom referred to as the head by some

It’s a Navy term – mostly used by Navy & Marines. The “head” was the forward, raised section of a boat where sailors would go to use the restroom. Normally a grate was there and was opened up to the ocean so the water would keep it somewhat sanitary.

Well thats what it was back then but now days it is a term of what they do in the bathroom if you know what I mean and sometimes the sink is called the sperm bucket thats all that I know I have friends that are in the marines so thats what they have told me