Bip39 implementation https://jaspermuxp089.yousher.com/top-5-online-bip39-generators-for-effortless-copyright-security Despite the fact that it uses BIP32 method you can nonetheless import BIP39 seeds into Electrum wallet. Also aside from BIp32 You can find BIP44 version which some wallet use for your technology of seeds. For words that have only three letters, there isn't a 4th letter. https://ragingbookmarks.com/story20673915/bip39-word-list-bip39-ian-coleman-for-dummies-https-www-youtube-com-channel-ucupxfytj0fb78sq55hu6ocw