In the Navy, the "head" is what we call the restroom (toilet). On Old Ironsides (the USS Constitution) you can see why the toilets were places at the head of the ship. It was done for... strategic purposes. You see, the bow hangs waaayyy out over the water. When I toured the ship, I took a peek at the toilet bench (there were several side by side) and when you look down where people would sit you see the water far below. The captain of the ship by the way also has his private toilet in back, also hanging out from the side of the ship over the water.
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Aren't you glad you asked?