This is the question I was taught while learning English in China
for finding the place to relieve oneself. We were taught that we
could either use the word "toilet" or "WC".
I remember our Chinese teacher was once asked to do interpretation
for a group of visiting Americans . When he came back, he
said to us "When he Americans want to use WC, they asked 'where
is the bathroom?', hahaha...that's interesting!" We all laughed with him.
Later on, I came across such words as "washroom" and "restroom",
thinking the former must be a room where foreigners wash their hands,
and the latter could be a waiting room in a railway station or airport where
people rest before departure. I did not figure out their real meaning until
after years later. Even today, the most popular Chinese dictionary still
has this definition for restroom: A room where people rest (in a public
facility or a government building , with a toilet attached inside the room.)
Though I do not say "WC" now in N.America, in my mind the room
where I am going to relieve myself is still "WC". Because it is hard
to forget a habit I learned at a younger age.
When I first came to Spain (many centuries ago), I heard the word 'Batter' meaning toilet. I was very surprised and often wondered about it until I saw the word written - 'water' (the Spanish pronounce the W as B). Then it dawned on me - 'Water' from the English 'water closet'.