The spelling is "Mastodon", like the extinct megafauna. The client also displays other ActivityPub feeds.
Personally I think "toot" is perfectly fine; no sillier than "tweet".
Toot is a fart
At least it's not as bad as Bluesky's skeet, I'll give it that
E: returning from a rabbit hole. Looks like Mastodon retired toot back in 2022 anyway (and skeet was never officially sanctioned by Bluesky)
The toot is moot.
If you want to follow me on Mastodon, BTW, you can find me at @masto@masto.masto.com.