Because your dick goes inside it and releases its juices causing relief and pleasure.
Pirates commonly referred to the toilet as the "head." This term originates from the location of the toilet on a ship, which was typically at the front, or "head," of the vessel. Using nautical terminology, they would say they were "going to the head" when they needed to relieve themselves.
Flight crews call them "Lavs"- short for lavatory. Naval aviators still call them the "Head".
A toilet in the U.S. Marines or U.S. Navy is traditionally known as a 'head', so someone who needs to go to the bathroom is "making a head call." The Army and Air Force makes do with the Boy Scout term "latrine."
In the Navy and Marine Corps, they are called 'The Head'
The toilet on a boat is referred to as the "head".
pull
School prank- Putting someones head in a toilet, then flushing.
Because one "toils" there.
TOILET
"The head".
Head
No, he goes down the sink