the.com/hippo

means A large, thick-skinned African mammal that spends most of its day in rivers and lakes, and is one of the most dangerous animals on the continent despite its dumpy appearance.

from Short for 'hippopotamus,' which comes straight from Greek 'hippopotamos' — a compound of 'hippos' (horse) and 'potamos' (river), literally 'river horse.' The Greeks weren't being whimsical for no reason: the animal lumbers around rivers like a bulky, snorting beast, and 'horse' was their go-to word for any large, powerful creature. The clipped 'hippo' is just modern convenience — nobody wants to say 'hippopotamus' twice in one sentence.