Native English speakers, do you ever say "fit-on room" instead of fitting room? Does it or does it not sound wrong/ not natural?

No, it’s not correct.

I’ve never heard that expression and it doesn’t sound natural at all.

Never heard that. It's a fitting room to me.

Fitting room. — a room to see if the clothing fits.

I've never heard this and probably wouldn't know what someone meant if they said it unless they pointed at a fitting room as they said it

Sounds like it might be an [eggcorn](https://en.wikipedia.org/wiki/Eggcorn) to me. Although "fit-on" doesn't really make syntactic sense either.

Just wrong.

No

Are you thinking of the phrase "try on" as in "we use the fitting room to try on clothing"? (We still don't refer to fitting rooms as "try-on rooms", but I think people might figure out what you meant if you said that, whereas I don't think they would understand "fit-on" at all.)

Fitting room, nothing else.

Lol that is cute but no

No

No, never heard it. We don't "fit-on" clothing. Clothing can fit on us, but usually we just say it fits us. Something that would make more sense, although it's not a real phrase either, would be a "try-on" room, a room in which we try on clothes.

Nope. Always fitting room, however, "fit-on room" gives enough context to know what you mean, you could also say "try-on room".

I have never heard anyone say this, and saying it aloud here in my living room, it feels wrong and completely unnatural.

As a New Zealander, this is just as incorrect as other people are indicating. Fitting Room is what it is called.

To my knowledge that isn't a thing. They are called fitting rooms where I'm from, both casually and professionally in the retail industry.

“Fitting room” exclusively. 

I say fitting

Never heard of a "fit-on" room. It's just incorrect (UK) A fitting room or a changing room would be the normal term.

No and most people likely wouldn’t understand what you’re talking about unless you were in a clothing store picking out clothes when you said it.?

fitting room is most common in American English. I've heard trial room abroad, and maybe try-on room. I've never heard fit-on room anywhere. but maybe if someone says fitting very fast and as "fittin" it sounds like fit-on?

Nope! If you don’t want to say “fitting room,” I’ve also heard people call it a changing room (because it’s a room for changing clothes).