Bip39 recovery seed word list https://www.tumblr.com/generalllamacolor/787594721599078400/can-you-depend-on-online-bip39-generators-a While it uses BIP32 system you could even now import BIP39 seeds into Electrum wallet. Also aside from BIp32 There's BIP44 Edition which some wallet use with the technology of seeds. For words that only have three letters, there isn't any 4th letter. As https://bookmarkpath.com/story20594768/bip39-algorithm-everything-about-bip39-word-list-txt-https-www-youtube-com-channel-ucupxfytj0fb78sq55hu6ocw