Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Thomas Crapper did not invent the flush toilet; it was invented by Sir John Harrington in 1596. Crapper, however, did much to increase its popularity and came up with some related inventions, such as the ballcock mechanism used to fill toilet tanks. He was noted for the quality of his products and received several Royal Warrants. He was not the origin of the word crap, but his name may have helped popularize it.