Toilets: Then and Now, Part 01; Toilet History
(Latin: toile to toilette in Middle French)
English borrowed the Middle French word toilette in the sixteenth century and eventually settled on the spelling toilet. The English word has at one time or another reflected most of the French senses; the "grooming" sense is still used, especially in expressions like "to be at one's toilet". All of these have tended to be transformed from "dressing room" through "dressing room with bath facilities" through "lavatory" and finally to "water closet", "women's room", "men's room", etc.
While English uses a French-word form to euphemistically designate this necessary facility, French repays the compliment by calling it le water-closet or le w.c.
If you consider the contribution of plumbing to human life, the other sciences fade into insignificance.
2. A room or booth containing the fixtures as described in number 1, above.
3. The act or process of dressing or grooming oneself, including bathing and arranging the hair; such as, "to make one's toilet"; "busy at his/her toilet".
4. Archaic: A dressing table.
5. In medicine, cleansing, as of an accidental wound and the surrounding skin, or of an obstetrical patient after childbirth.
6. Etymology: from about 1540, "a cover" or "bag for clothes", from Middle French toilette, "a cloth, bag for clothes"; diminutive of toile, "cloth, net". The evolutionary sense is the "act" or the "process of dressing" (1681); then, "a dressing room" (1819); especially, one with a lavatory attached; then it included "a lavatory" or "porcelain plumbing fixture" (1895).
A similarly functioning device, known as a water closet, is recorded as early as 1755.
Euphemisms for "toilet" abound around the world
Americans weren't the first to use euphemisms to refer to the toilet. The toilet and/or the "outhouse" have at one time or another been called the "House of Honor" (by the ancient Israelites), the "House of the Morning" (by the ancient Egyptians), the "garderobe" (literally, "cloakroom"), the "necessarium", the "necessary house", the "privy" (that is, the "private place"), the "jakes", the "john", the "W.C." (for "water closet"), "Room 100" (in Europe), the "lavatory", the "closet", the "boys' room", the "girls' room", the "mens' room", the "ladies' room"; and many other terms.
There is no "real" word for the place where one deposits one's bodily wastes. "Toilet", which is now thought of as the "official" term, is itself a euphemism.
Originally, toilet was the process of dressing, as in, "the lady has just completed her toilet".
Before toilet assumed its present meaning in the early twentieth century, the accepted technical term for the "toilet" was the vaguely disgusting but still euphemistic "bog-house". So, we have something for which there are polite terms and impolite terms, but no simply correct term.