Loo meaning ‘toilet’ was first recorded in the early 1930s; the origin of the word is uncertain, although various theories have been put forward. One suggests that the source is Waterloo, a trade name for iron cisterns in the early 20th century. Another idea is that it is from the former French euphemism for a latrine, lieu d'aisances (literally ‘place of ease’), an expression which could have been picked up by British troops in France during the First World War. Yet another theory traces the term back to the cry gardy loo! (from French gardez l'eau ‘beware of the water’), formerly uttered by people who were about to throw the contents of their chamber pots out of their windows.

C17: abbrev. of obs. lanterloo from Fr. lanturlu, a meaningless song refrain.