the.com/rhino

means A large, thick-skinned, horn-nosed mammal — also casual slang for the animal's horn material or, separately, for cash.

from Short for 'rhinoceros,' which comes from Greek 'rhis' (nose) plus 'keras' (horn) — literally 'nose-horn.' The clipped slang form 'rhino' for the animal shows up in English by the 1800s. Oddly, 'rhino' was also old British slang for money, recorded even earlier, in the 1600s — that usage's origin is uncertain, and it's unrelated to the animal; some guesses tie it to Greek 'rhinos' again, perhaps joking about paying 'through the nose,' but it's folk speculation, not confirmed fact.