Where did the practice of waving your hand under a bath room stall begin to attract others?

It seems very dangerous that some one might pee on itWhere did the practice of waving your hand under a bath room stall begin to attract others?
Don't know but someone would get their had smashed.Where did the practice of waving your hand under a bath room stall begin to attract others?
If you're in a bathroom stall you probably aren't peeing.
I dont know...weird.