Why do we say razzle-dazzle instead of dazzle-razzle? Why super-duper, helter-skelter, harum-scarum, hocus-pocus, willy-nilly, hully-gully, roly-poly, holy moly, herky-jerky, walkie-talkie, namby-pamby, mumbo-jumbo, loosey-goosey, wing-ding, wham-bam, hobnob, razza-matazz, and rub-a-dub-dub? I thought you'd never ask. Consonants differ in "obstruency"—the degree to which they impede the flow of air, ranging from merely making it resonate, to forcing it noisily past an obstruction, to stopping it up altogether. The word beginning with the less obstruent consonant always comes before the word beginning with the more obstruent consonant. Why ask why?
Steven Pinker, The Language Instinct: How the Mind Creates Language
language, linguistics, phonetics