A swimming Pool, also known as a potential shark tank, the septic tank, and/or the public toilet is a semi-portable amusement(as in, it will not fit into some compact cars) which enables the user to swim in ankle-deep liquid, which is often included with a diving board, followed by a visit to the Hospital and/or death.
The term "swimming pool" was first used after King Arthur the IVIIVXCI....oh who gives a frick? decided he would be the ruler of England and since he named his son "swimming" because he thought it was awesome, and he named his daughter "pool" because he hated her guts.
It happened one night when King Arthur came home from heavy drinking and decided to sleep on the roof, which was where wasps' nests were all the time. When he woke up the next morning, he found himself stung in several places, along with a heavy hangover that made him want to punch the air repeatedly for no reason.
After he got off the roof he looked at his kids and finally named them, because they had been waiting to be named for 32 years, and so they were just called "Thing #1" and "Thing #2" in the past and no one seemed to care.
The term came into use when he told everyone about it and they all thought it was a good idea, except for this one man named Bob Saget, who was hanged in the middle of the desert later.