Bip39 rust crate https://www.anobii.com/en/01000289012ff9b293/profile/activity While it makes use of BIP32 process you can still import BIP39 seeds into Electrum wallet. Also besides BIp32 There's BIP44 Model which some wallet use for your generation of seeds. For words that only have three letters, there isn't a 4th letter. As an example https://bookmarkbells.com/story20546565/bip39-word-list-txt-how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-english-word-list-https-www-youtube-com-channel-ucupxfytj0fb78sq55hu6ocw