Download bip39 wordlist https://squareblogs.net/edelinepge/using-python-to-produce-a-bip39-mnemonic-a-developers-point-of-view This is certainly why you must come up with a backup of your seed phrase making use of metallic copyright wallet like Coinplate, that happen to be 100% chrome steel and BIP39 compatible. For words that have only 3 letters, there's no 4th letter. For instance https://zenwriting.net/keenanctdp/how-to-create-a-bip39-seed-a-step-by-step-guide