Gosh, onomatopoeia is hard to spell, but it just means a word which sounds the same as the thing it describes.
Like hiccup and hum. That sort of thing.
But of course nothing's that easy.
Take a clock. They say (more or less) tick-tock in English and Filipino (tick-tack is generally commoner, elsewhere), but in Albania clocks run in waltz time: tik-tak-tok, tik-tak-tok.
This is very odd, I think, given that all early clocks had pendulums.
Or how about sheep. English sheep are supposed to bleat, but I've never heard a sheep say bleat in my life. Sheep round here go merrrrrr!
Sometimes the difference between an obvious attempt at onomatopoeia and the actual sound of the object is easy to explain. Frogs do go ribbit ribbit in America, but not here in England: our common species of frog goes (pretty much) croak.
And of course some sounds are just too difficult or spitty: no one wants to stop in the middle of a sentence to do an authentic imitation of a pig's grunt.
All the same, onomatopoeia gets everywhere, sometimes in quite subtle ways. All sorts of words, like laughter, or chain, have I think an echo of their sounds about them.
It's one of the things that make language so magical and evocative.
Thing To Do Today: listen out for onomatopoeia. This word is Greek, from the words onoma, which means name and poiein, to make.