"Toilet" & "Lavatory" originally meant the place one goes to wash [see Susan Coolidge's "What Katy Did at School" for an example of the latter use]; but became unusable for such meanings because they became euphemisms for the shithouse

([or, perhaps still slightly euphemistic] water-closet; earlier jakes, on which Shakespeare punned regarding the name of a character in As You Like It; or privy [ie private place]; or latrine [generally a hole-in-ground earth closet]; or, idiomatic, bog);

to be succeeded by words of similar meaning like washroom or bathroom; or, even more evasively, restroom. Or the U [in the Nancy Mitford sense of Upper-class] loo, of disputed etymology, perhaps from French l'eau, or the odd 0-0 (supposedly a pun on deux-eaux = two waters), preceded bu definite article before vowel l'.

Some day I suspec wet might run out of available euphemisms & have to return to good old shithouse, eh?

Appropriate, perhaps, to quote here: "These are deep waters, Watson."

LoL [or LoO?]

~M~