system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we say "Zack and Cody" instead of "Cody and Zack" or "Mary-Kate and Ashley" instead of "Ashley and Mary-Kate"? Does it have something to do with our brains or the way a sentence rolls off our tongues?
gpt
These are called frozen binomials and are pairs that usually follow a specific order, f.i "pots and pans" instead of "pans and pots". Usually it's just what sounds better. while not absolute the general rules seem to be

* short sounds before long sounds
* Few syllables before many syllables
* Sounds that are easy to say before harder combinations
* Alphabetical if neither apply. 

So, Zack and Cody rolls better with 1 vs 2 syllables instead of Cody and Zack with 2 vs 1. Mary-Kate and Ashley has 2 short 1 syllable sounds vs 2 longer sounds in Ashley.