That's true, but those uses of the word are pretty obscure. I would say the most common meaning of "toot" in the UK is the noise a horn makes, especially a bicycle/car/train horn.
Some of us who have been on Mastodon for a few years now insist on calling them toots, despite the official renaming in the original Mastodon repo. A toot is the sound elephant friend (our mascot) makes with their trunk.
Also it's silly and all of the other silly associations you have with it are a plus. "Twitter", "tweet", "google", "facebook", "amazon", "apple", "mac", "tumblr", "kindle" are all also pretty stupid names we've just gotten used to, but "toot" is OUR stupid name, and we made it ours, and if its silliness delays the corporate takeover of Mastodon, that's a huge plus.
It's pretty funny due to it's usage in UK slang. It can mean everything from smoking a cigarette, to snorting cocaine, to oral sex.