Bip39 or slip39 https://padlet.com/alexzhiglatyzbugt/bookmarks-68ta5bpd7yy3slro/wish/PVKBQO1nwDeMWj5x While it utilizes BIP32 approach it is possible to even now import BIP39 seeds into Electrum wallet. Also besides BIp32 You can find BIP44 Edition which some wallet use for your generation of seeds. For words that only have 3 letters, there is no 4th letter. https://bookmarking1.com/story20652863/bip39-javascript-the-5-second-trick-for-bip39-compatible-wallet-https-dzen-ru-bip39-phrase-com