Historical in Edinburgh, used as a warning to people below that slops were about to be thrown from a window into the street
Origin of gardyloo; from French garde à l'eau, beware (of) the water
- (obsolete) Used by servants in medieval Scotland to warn passers-by of waste about to be thrown from a window into the street below. The phrase was still in use as late the 1930s and '40s, when many people had no indoor toilets.
French garde à l'eau translated means "beware of the water."