That is someone's theory? That's what 'onomatopoeia' means.
Read the link I provided, he does a much better job there. If you don't want to read all of it just search for "Now, remember I said the third thing you have to do in science is show that this is not just some quirk.", and read from the top of that section.
'slush' is onomatopoeic. Is 'axe'? How about 'milk' or 'mother'?