Amusingly, onomatopoeia (itself a difficult-to-pronounce word) refers to words that sound like the thing they’re referring to. Well-known instances of onomatopoeia include whiz, buzz, snap, grunt, etc. Example: The excellent children's book Click, Clack, Moo: Cows That Type. 'Farmer Brown has a problem. His cows like to type. All day long he hears: Click, clack, moo. Click, clack, moo. Clickety, clack, moo.'