The room used for defecation is almost always referred to by euphemism.
In Britain this still means a room containing a bath.
This used to mean no more than a room used for washing. It was identical to washroom. "From Late Latin lavātōrium, from Latin lavāre to wash."
The word toilet is a euphemism. It previously was used to refer to the early morning routine of preparing for the day by washing, combing hair and applying various potions. So far as I know it did not include defecation and was therefore a perfectly innocuous and polite subject for general conversation. It can be startling to read the word when used in that sense in older books or artworks.
A woman at her toilet - Titian.
A euphemism in Britain (and some European countries) was water closet, nowadays abbreviated to W.C. Taken literally it implies no more than a small room provided with a supply of water - nothing offensive there.
The British National Corpus provides these counts
It seems that euphemisms must be constantly renewed by replacement as they become tainted by association with the taboo subject. This replacement proceeds at different rates in different countries, cultures or social groups. This means that, in time, new words must also be found for the existing meanings of words like convenience.