Americans don't like speaking of the "toilet" unless we are referring to the actual plumbing fixture, so we call the room where the toilet is located a "bathroom" even when we know it's impossible to bathe there. Some people refuse to say toilet at all and call the fixture a "commode".
Because much of the world uses English as a modern day Lingua Franca there are now such things as European English, Asian English, and so on:
Public toilets are known by many names in different varieties of English. One of the more formal circumlocutions is "public convenience", as in the Guilford Place public conveniences, an architecturally valuable example.
In [US] American English, "restroom" usually denotes a toilet facility designed for use by the public. However, "bathroom" is also commonly used. "Comfort station" sometimes refers to a visitor welcome center such as those found in national parks.
In Canadian English, public facilities are always called "washrooms". The word "toilet" generally denotes the fixture itself rather than the room. The word "washroom" is never used to mean "utility room" or "mud room" as it is in some parts the United States. "Bathroom" is generally used to refer to the room in the home that contains a bath or shower.
In Britain, Australia, Hong Kong, Singapore, and New Zealand, the terms in use are "public toilet", "public lavatory" (abbreviated "lav") and more informally, "public loo". A "bathroom" is a room containing a bath, a "washroom" is a room for washing hands, and a "restroom" is a room to rest in when tired; none of which would necessarily contain a toilet. As public toilets were traditionally signed as "Gentlemen" or "Ladies", the colloquial terms "the Gents" and "the Ladies" indicates the facility itself. The British Toilet Association, sponsor of the Loo of the Year Award, refers to public toilets collectively as "away from home" toilets.
In Philippine English, "comfort room", or "C.R.", is the most common term in use.
In continental Europe, both "toilet", a translation of the French les toilettes, and "WC" (abbreviation for "water closet", an older term for the flush toilet) are common.
Mosques, madrassas (schools) and other places Muslims gather, have public sex-segregated "wash rooms" since Islam requires specific procedures for cleansing parts of the body before prayer. These rooms normally adjoin the toilets, which are also subject to Muslim hygienical jurisprudence and Islamic toilet etiquette.
The term "water closet" ("WC") was an early term for an interior or exterior room with a flushing toilet in contrast with an earth closet usually outdoors and requiring periodic emptying as "night soil". Originally, the term "wash-down closet" was used. The term "water closet" was coined in England around 1870. It did not reach the United States until the 1880s. Around this time, only luxury hotels and wealthy people had indoor private bathrooms. By 1890 in the US, there was increased public awareness of the theory of disease and of carelessly disposed human waste being contaminated and infectious.
Originally, the term "bath-room" referred only to the room where the bathtub was located (usually a separate room not housing a toilet), but this connotation has changed in common North American usage. In the UK, the terms "bathroom" and "toilet" are used to indicate distinct functions, even though bathrooms in modern homes often include toilets. The term "water closet" was probably adopted because in the late 19th century, with the advent of indoor plumbing, a toilet displaced an early clothes closet, closets being renovated to easily accommodate the spatial needs of a commode. Early indoor toilets had in fact been known as garderobes because they actually were used to store clothes, as the smell of ammonia was found to deter fleas and moths.
The term "water closet" is still used today in some places, but it often refers to a room that has both a toilet and other plumbing fixtures such as a sink or a bathtub. Plumbing manufacturers often use the term "water closet" to differentiate toilets from urinals. American plumbing codes still refer to a toilet as a "Water Closet" or a "WC". Many South American countries refer to a toilet as a "water" or "WC". The Royal Spanish Academy Dictionary accepts "váter" as a name for a toilet or bathroom, which is derived from the British term "water closet". In French, the expression aller aux waters ("to go to the waters") has now become obsolete, but it also derives from "water closet". "WC" is still used in the French language, although not as common as the term "toilet", and pronounced as "VC", a shortened version of "double V C". In Germany, the expression "Klo" (first syllable of "Kloset") is still used, though "WC" is more common. In Dutch and Swiss German, using the term "WC" is common.
In many Asian countries and China in particular, "WC" is used as a universal name for the toilet; many Chinese people will make a hand sign with the forefinger and thumb held in the shape of a "C" while the remaining 3 fingers of the same hand are extended to represent a "W", thus indicating where they are going or perhaps to explain where someone has gone.