Frédéric Jacobs on Nostr: The words are an encoding of bits derived using a hash function from the ZRTP ...

The words are an encoding of bits derived using a hash function from the ZRTP confirmation which contained the call's shared key.

The words used for SAS strings were cleverly chosen with the help of computational linguist Patrick Juola to maximize the phonetic distance between them.

https://en.wikipedia.org/wiki/PGP_word_list
https://www.mathcs.duq.edu/~juola/papers.d/icslp96.pdf