Why is a bathroom on a boat called the head?
When On a Boat Be Sure to Use Your “Head”
Head is a much used maritime word meaning the top or forward part. Head was also the name given to that part of the older sailing ships, forward of the raised section near the bow or forward part of the boat called the forecastle.
So when someone said they were going to the head it meant they were going to the forward part of the boat. The sailors would climb down onto an area floored with a grating to relieve themselves. The grating allowed the open sea to help keep the area clean. The name has been largely retained among seamen, even in these days of modern toilets and modern flushing devices.