Is it ensure, insure, or assure?
1530s, "cover or bag for clothes," from Middle French toilette "a cloth, bag for clothes," diminutive of toile "cloth, net" (see toil (n.2)). Sense evolution is to "act or process of dressing" (1680s); then "a dressing room" (1819), especially one with a lavatory attached; then "lavatory or porcelain plumbing fixture" (1895), an American euphemistic use. Toilet paper is attested from 1884 (the Middle English equivalent was arse-wisp). Toilet training is recorded from 1940.