Bip39 onekey https://andersonsaeu988.iamarrows.com/bip39-generator-online-the-best-devices-for-secure-wallet-creation Even though it uses BIP32 process you can even now import BIP39 seeds into Electrum wallet. Also other than BIp32 There's BIP44 version which some wallet use for that generation of seeds. For words that only have three letters, there is absolutely no 4th letter. One ex... https://indexedbookmarks.com/story20740842/bip39-react-bip39-compatible-wallet-can-be-fun-for-anyone-https-x-com-tundra838554