The term may have originated in Windsor Ontario in 1970 when I threw a turd into a fan to impress my sisters girl freind. It did not impress her but when her brother heard about it we became freinds. Anyway this question reminded me of a song we used to sing - cocktails gingerale five cents a glass if you get hit with a bucket of sh*t be sure to close your eyes. Cheers!
There was an incident that happened in a bar one time, a guy walked into the bar and orders himself a drink then feels his need to use the can. He could not find a washroom on the ground floor so he goes up a stairs, looking around there is no bathroom upstairs neither so then he notices a hole in the floor and decides that will serve the purpose. Returns back downstairs and finds the bar is vacated. "Where did everyone go?" he asks the bartender. "Where were you when the shi# hit the fan?" the bartender asks him.
That is the original story that happened during the late 1800s