The English language is a wonderful thing, and we know some rules without knowing we know them.
‘Have you ever heard that patter-pitter of tiny feet? Or the dong-ding of a bell? Or hop-hip music? That’s because, when you repeat a word with a different vowel, the order is always I A O. Bish bash bosh. So politicians may flip-flop, but they can never flop-flip. It’s tit-for-tat, never tat-for-tit. This is called ablaut reduplication, and if you do things any other way, they sound very, very odd indeed.’ From ‘The Elements of Eloquence’ by Mark Forsyth.
