Opinions can differ Rowantree but are roughly similar
The British word for toilet, “loo”, derives from the French - In medieval Europe people had little conception of hygiene and threw the contents of their chamber pots out the window into the street below. In France the practice was preceded by “garde a l’eau!” (“watch out for the water!”). In England, this phrase was Anglicised, first to “gardy-loo!”, then just “loo”, and eventually came to mean the toilet/lavatory itself
I particularly like, however, the response which was “Haud yer han’ “ or “hold your hand” which you hoped would give you a few precious seconds to duck into a doorway for cover!