Wikipedia: approximately 26th century BC: Flush toilets were first used in the Indus Valley Civilization. The cities of Harappa and Mohenjo-Daro had a flush toilet in almost every house, attached to a sophisticated sewage system.
Who knew? I didn't. Thank you for this question; I have learned something new today.
John Crapper....in Robin Hood Men in Tights, when King Richard returned from the Crusades and found out his brother John was treating the people poorly he said "from this day forward...ALL toilets across the land shall be known as ...The John!!!"