As long as there have been sailors, there’s been the need for them to “go to the bathroom.” Of course it wasn’t called that on the ships before or after the time of Columbus. In the early days of sail, when ships first ventured out of the sight of their own lands, they called it many things, mostly vulgar things, but it all meant the same thing.
On ships of sail, the crew members took their “needs” forward, to a place near the bowsprit, a spar that helped lash-up the foremast, a place near the ‘head’ of the ship. There, they would find a plank stretching out from the bow. It would have a hole cut in it to accommodate that part of the body that did the business. It was located at the ship’s figurehead, or if a ship didn’t’ have a carved persona at her stem, merely the “head.”
A ship’s bathroom has been called “the head” ever since. Certainly it’s an archaic term that has no literal meaning on modern vessels of any size. But like other colloquial terms of seafarers (and in other professions and industries), the original name stuck.
Naval ships today use seawater, or brine, for flushing real toilets that are located liberally throughout the ships. Sailors no longer have to go to the bow and hang themselves over open water to take care of business. Waste on naval ships is held in tanks until the vessel is well out to sea, at which time it is disintegrated in a special treatment plant aboard, and discharged overboard.
But such discharges anywhere near the shores of the United States are highly illegal. Pleasure boats are required to have “holding tanks” on board, and marinas are required to provide “pumping out” services – most provide them free – which sends the waste into the local sewer or septic systems, thus saving inland and coastal waters from further pollution.
Despite these modern ways of doing what sailors have always done, and despite the passage of hundreds of years, the toilet on board is still “the head,” and “the head” it will always be.
