An onomatopoeia is a word “which imitates the natural sounds of a thing. It creates a sound effect that mimics the thing described….” 
Bees buzz, cows moo, horses whinny, etc.
However, there are some words that sound so much not like what they mean that you can get yourself in trouble using them.
“My, what a pulchritudinous woman you are!”
to your date, chances are you’re going to get slapped – even though you shouldn’t. Pulchritudinous actually means:
“having great physical beauty.” 
Inquiring minds want to know. 
 And did he ever have a date?