I’m wouldn’t place my bet on Mr. Tom Crapper. There are two famous “Johns” in toilet history. Sir John Harrington is credited with creating the first “flushing” pan (toilet) and Edward John made “potties” for the American public- Edward Johns and Co Sanitary Pottery . It seems more likely that the term John came from one of these fine fellows.
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Armitage Shanks is a famous UK-based business whose name has been fouled in one way or another by just about every UK based resident, since they manufacture home and publicly-used sanitary ware. Their canalside factory at Armitage, Staffordshire dates back to 1817 and became noted for sanitary ware manufacture under the management of Edward Johns, also given as the source of the Americanism “the john.” The explanation would gain credence if Armitage Shanks were large 19th century exporters to the old colony. The Staffordshire area is noted for several similar businesses including nearby Spode, and a little further away, Wedgewood. It was Josiah Wedgewood who sponsored the building of the particular canal here which represented a vast improvement for the transport of pottery compared to the previously used packhorses and carts.