Bip39 https://orcid.org/0009-0002-7964-3457 Although it makes use of BIP32 strategy it is possible to still import BIP39 seeds into Electrum wallet. Also besides BIp32 There may be BIP44 version which some wallet use for the technology of seeds. For words that only have 3 letters, there's no 4th letter. For example https://www.gamespot.com/profile/pothirpeib/