Why is the toilet called the John?

Answer 1

Probably after the 'inventor' of the water closet, John Harrington.

Eighteenth century was a century of toilets. Despite invention of water closet by John Harrington in 1596, which was, costing only 6 shillings and 8 pence this was not adopted on a large scale for almost 182 years. ...During this period people used earth closet. In these toilets instead of water earth was used. So the problem of cleaning remained. The world also saw development of Pan closets - which like cigarette ashtray threw the material at the bottom. This too required manual cleaning. At the same time chamber pots, close stools, open defecation remained. In comparison to this, Harrington's toilet under the name Angrez was being used in France, though not introduced on a large scale in England. In 1738 JF Brondel introduced the valve type flush toilet. Alexander Cummings further improved the technology and gave use a better device in 1775. In Cumming's design water was perennially there in the toilet so it suppressed odors. Still the working of the valve and foolproof inlet of water needed further improvements. In {1777;} Joseph Preiser provided the required improvement. Then Joseph Bramah in 1778, substituted the slide valve with crank valve, It seemed then that the technology of pour flush was now perfected. No the world was yet to witness further technological developments. In 1870, SS Helior invented the flush type toilet, called optims - an improvement over Blummer's design.