Bip39 crate https://padlet.com/alexzhiglatyzbugt/bookmarks-68ta5bpd7yy3slro/wish/PVKBQO1nwDeMWj5x Even though it works by using BIP32 approach you could even now import BIP39 seeds into Electrum wallet. Also apart from BIp32 You can find BIP44 Edition which some wallet use with the generation of seeds. For words that have only three letters, there isn't any 4th https://canvas.instructure.com/eportfolios/3396498/ricardooxtv236/bip39-generator-online-the-very-best-tools-for-secure-pocketbook-development