Why is the term john used for toilet?

"The John" for Sir John Harrington

The flushing toilet was invented in 1596, not by Thomas Crapper as most people think, but by Sir John Harington. Harington, a British nobleman and godson of Queen Elizabeth I, invented a valve that when pulled would release water from a water closet. Sir John recommended flushing the toilet once or twice a day, although with our modern technology, we know that is probably not sufficient. (Rumor has it that, in Robin Hood's day, King Richard the Lionheart - angry with how his brother, Prince John, ruled the country while the King was gone, named fair toilette, 'the john' - AKA as 'the Jon' to you folks.)

Answer Inventor of first flush toilet.

Sir John Harrington invented the first flush toilet in the late 1500's. I have even heard that he installed it for Queen Elizabeth 1st, and she affectionately referred to it as her "John", but have no idea if that is true. I believe he actually installed the first toilet in his own mansion.