When we received a coupon for something called "bath tissue," my wife asked, as anyone might, what in the world that was. In just few years, "toilet paper" has evolved into "toilet tissue," then "bathroom tissue" and now, at least according to one manufacturer, "bath tissue."
The word toilet was, of course, once itself used as a euphemism, although I have no idea what it was a euphemism for. The English language seems to have no noneuphemistic words to refer to that particular room of the house. The English word toilet comes from the French word for the process of dressing, toilette. Toile is the French word for cloth.
As children, my sisters and I used to giggle when pointing to our mother's bottle of "toilet water," but the term refers to a lightly scented perfume. Women used to have bottles of this on their dressing tables, but we don't hear the term much anymore. Nor do we hear the phrase "toilet call." This was what it was called when a fashionable lady received visitors in her dressing room. The word toilet came to refer to other things, and now even that polite word is considered a bit uncouth.
We have had scores of euphemisms for "that little room." Hugh Rawson presents an exhaustive, if still incomplete, list of them in his Dictionary of Euphemisms and Other Doubletalk. A few of these include ajax, altar room, bathroom, can, comfort station, facility, gab room, holy of holies, John, marble palace, necessary house, office, poet's corner, privy, rest room, sanctuary, tearoom, washroom and WC. Each of us probably has our own favorite.