Bip39 implementation https://list.ly/abregeouoh Though it takes advantage of BIP32 process it is possible to however import BIP39 seeds into Electrum wallet. Also apart from BIp32 There exists BIP44 Model which some wallet use for that generation of seeds. For words that have only 3 letters, there is no 4th letter. https://redhotbookmarks.com/story20773850/official-bip39-list-bip39-passphrase-generator-options-https-x-com-tundra838554