Why is it called a "loo?"

The British word for toilet, "loo", derives from the French "garde a l'eau!" 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. The American word for toilet, "john", is called after the John Harington who in 1596 invented an indoor water closet for Queen Elizabeth I