Perhaps no word in English has undergone more transformations in its lifetime than ‘toilet’. Originally, in about 1540, it was a kind of cloth, a diminutive form of ‘toile’, a word still used to describe a type of linen. Then it became a cloth for use on dressing tables. Then it became the items on the dressing table (whence ‘toiletries’). Then it became the dressing table itself, then the act of dressing, then the act of receiving visitors while dressing, then the dressing room itself, then any kind of private room near a bedroom, then a room used lavatorially, and finally the lavatory itself.
Bill Bryson, At Home: A Short History of Private Life, 2010