This is clearly subjective, but some words really sound like the thing they describe (personal favorites: puffin; bulbous; fidgeting). Do you have an example of such a word (or, alternatively, of a word that sounds like the exact opposite of what it refers to)? What do you think creates this effect?
Reading the instructions for today’s prompt, I recalled one of the books I have read. There was a line in that book talking about the silence at home broken by the “whirring of the mixer”. I was a bit surprised about how whir sounds so much like the sound of an actual mixer.
I think the same is true for hum. Or click. Or boom. Or buzz. Hum sounds like hmmmm-ing. Click your tongue and it sort of sounds like click. Boom perfectly illustrates someone with a booming voice. And a buzzing bee clearly buzz.
As to what creates that sort of effect, I guess it’s because those words were designed to mimic the sound of what thing it stands for. I don’t know, I don’t give much thought to it.