Bip39 eth https://padlet.com/alexzhiglatyzbugt/bookmarks-68ta5bpd7yy3slro/wish/PVKBQO1nwDeMWj5x Although it takes advantage of BIP32 process you could nonetheless import BIP39 seeds into Electrum wallet. Also apart from BIp32 There's BIP44 version which some wallet use to the era of seeds. For words that have only three letters, there's no 4th letter. By way of example https://bookmarkinglog.com/story20448592/bip39-compliant-passphrase-helping-the-others-realize-the-advantages-of-bip39-passphrase-https-cutt-ly-uryc5rw7