It is a very good question.
I think all these fancy names were born out of hypocricy.
And they can mean different things or nothing in different countries.
In Europe - W.C., Toilet/Toilettes or 00. (Here "bathroom" is a part of a flat, where you take a bath etc.).
In GB/Australia - Toilets, Public Toilet, Public Lavatory ("Bathroom" is a room containing a bath).
In Canada - "The Ladies' Room", "The Men's Room" ("Bathroom" means the same as in Europe).
So, if you travel a lot, you can get confused and even face serious problems explaining what place would you like to find.