This has been bugging me ever since the discussion so I looked it up.
Ref:
Online Etymology Dictionary
toilet (n.)
1530s, earliest in English in an obsolete sense "cover or bag for clothes," from Middle French toilette "a cloth; a bag for clothes," diminutive of toile"cloth, net" (see
toil (n.2)). Toilet acquired an association with upper class dressing by 18c., through the specific sense "a fine cloth cover on the dressing table for the articles spread upon it;" thence "the articles, collectively, used in dressing" (mirror, bottles, brushes, combs, etc.). Subsequent sense evolution in English (mostly following French uses) is to "act or process of dressing," especially the dressing and powdering of the hair (1680s); then "a dressing room" (1819), especially one with a lavatory attached; then "lavatory or porcelain plumbing fixture" (1895), an American euphemistic use.