"Bathroom" and "restroom" are only used in American English. In other English-speaking countries, a bathroom contains a bath, and a restroom sounds like somewhere to go if you're tired.

"Toilet" is also a euphemism, it's Middle French for a type of cloth.

So is "lavatory", it means wash room.

I can't think of a word that isn't vulgar or a euphemism.

"Toilet" is not a euphemism:

"Toilet" was by etymology a euphemism, but is no longer understood as such. As old euphemisms have become the standard term, they have been progressively replaced by newer ones, an example of the euphemism treadmill at work.

https://en.wikipedia.org/wiki/Toilet#Contemporary_Use

"Crapper" is not a euphemism. It's the name of the man who invented the siphonic flush toilet:

https://en.wikipedia.org/wiki/Thomas_Crapper

You forgot:

Washroom. Lavatory. Outhouse. Mens' room. Little girls' room room. Potty. Half bath. And many more (mostly NSFHN).

I suspect there's a deep reason for all the different words, probably because of the basic nature of what goes on within such rooms. I wouldn't be surprised if other languages have the same profusion of synonyms.

> I wonder if other languages have such an array of words for a toilet, and how much confusion they cause for foreigners.

Let me try in Spanish: servicio, baño, excusado, w.c, mingitorio, tigre (this is slang)

Do you think our culture is going to be uplifted somehow if we all switch to calling it "the shitter"?

In Portuguese, "banheiro" uses the exact same euphemism as bathrooms.