Ooh I have know a lot of these...

Bugbear: A brutish goblinoid which has no association with bugs or bears.

Crawling Claw: It’s makes sense as the name for a severed hand animated by necromancy, but is terribly uncreative

Dragon Turtle: It’s a gargantuan turtle that can eat ships whole and breathes out steam. What else did you expect?

Drider: This is kind of like a spider centaur; a drow whose legs is replaced by a giant spider body but it’s upper half remains drow. The name is literally just a portmanteau of “drow” and “spider”.

Flameskull: It’s a giant flying skull that’s on fire. Suiting, but horribly uncreative.

Gorgon: This would make sense if I was describing a Medusa or the ones from Greek mythology, but in the Monster Manual it is the name of an iron bull which spews out poisonous gas. For some reason WotC stole name of a famous mythological creature to describe an entirely different creature which has no association to the creature the original name was of.

Lycanthropes: Literally means “wolf man”, but the thing is that 4 out of 5 of the “lycanthropes” are other were animals which aren’t wolf based.

Purple Worm: Because everyone could perfectly be able to tell that this is the name of CR 15 monster which is larger than a house, right?

Roc: It sounds like it should be describing a rock monster, but this is actually the name of a giant flying bird which can carry away elephants.

Salamander: When I think salamander, I think of little amphibians, not human sized elemental made of pure fire which have nothing to do with actual salamanders.