> Add the propensity to colloquially grant newly discovered things names that borrow from existing things: sea cow, catfish, etc. so why couldn’t there be something called a tree octopus?

There could be. The name of the animal isn't what gives the lie away.

Today I learned that a tree crab is a thing. I knew a tree lobster was a thing. There is something that could plausibly be called a tree clam.