For centuries there was the practice of farmers coming into the towns, villages, and cities to empty urban outhouses of their nightsoil, as it was called, to use as fertilizer for their crops. As this free service wasn't always guaranteed, there were very ambitious men who, for a fee, would provide this service regularly to the aristocratic and wealthy and then turn around and sell it for a small fee as fertilizer to the farmers as well. Don't know what these gentlemen were called, though, except for smelly...or how 'bout septic couriers?