Bip39 rules https://collinmmss433.lucialpiazzale.com/from-concept-to-fact-generating-bitcoin-addresses-with-bip39 BIP85: A more moderen proposal enabling the deterministic derivation of various BIP39 mnemonic seeds from the master seed. For words that only have three letters, there isn't any 4th letter. One example is Along with the word “add”, there isn't any additional letters after... https://funny-lists.com/story21706193/bip39-english-word-list-a-secret-weapon-for-bip39-mnemonic-https-linktr-ee-bip39