" And at the risk of sounding like Andy Rooney on Sixty Minutes, have you ever wondered why we say fiddle-faddle and not faddle- fiddle? Why is it ping-pong and pitter-patter rather than pong-ping and patter-pitter? Why dribs and drabs, rather than vice versa? Why can't a kitchen be span and spic? Whence riff-raff, mish-mash, flim-flam, chit-chat, tit for tat, knick-knack, zig-zag, sing-song, ding-dong, King Kong, criss-cross, shilly-shally, see-saw, hee-haw, flip-flop, hippity-hop, tick-tock, tic-tac-toe, eeny-meeny-miney-moe, bric-a-brac, clickety-clack, hickory-dickory-dock, kit and kaboodle, and bibbity-bobbity-boo? The answer is that the vowels for which the tongue is high and in the front always come before the vowels for which the tongue is low and in the back. "

― Steven Pinker , The Language Instinct: How the Mind Creates Language