YOU CAN LISTEN TO HIP HOP, but not hop hip. You can hear the pitter patter of tiny feet, but never the patter pitter. You can hear chit chat turning into a right ding dong, but never chat chit turning into a dong ding.
Reduplicatives, they’re called, these doubled-up words with a single changed syllable. And the thing about reduplicatives is that the vowels always follow this sequence:
i a o
Flip flop. Flim flam. Tit for tat. Mishmash. Sing song. Knick knack. Ping pong. Tittle tattle. Wishy washy. Usually they only come in pairs, but even the rare three-legged versions follow the same rule.
Bish bash bosh.