The following passage is taken from an article by Celeste Olalquiaga entitled "Object Lesson/Abject Object", where she discusses the origins of the toilet and the sewage system, going as far back as 1700 for clues. Here is how the word "toilet" began :
"...Quite different [to the fate of the bidet] was the fate of that lasting invention -- toilet paper. Evolving from the fourteenth-century 'toilette' or 'tellete' - a piece of cloth used for wrapping merchandise that often included objects of personal care (from 'toile', cloth, and 'tisser', weaving) - 'toilette' was gradually applied to the elements and very act of washing and grooming, producing such well-known items as 'savon de toilette', 'eau de toilette' and in 1902, 'papier toilette'.
In 1945, probably as a contraction of the term 'cabinet de toilette', 'toilette' became a euphemistic name for that most denigrated of spaces, les toilettes, the WC, john, can, restroom, comfort station, girls' - or boy's - room, etc."
So, there you go.