Bip39 list github https://padlet.com/alexzhiglatyzbugt/bookmarks-68ta5bpd7yy3slro/wish/PVKBQO1nwDeMWj5x The last step of BIP-39 is creating the actual binary seed which can be then used as being a learn key in BIP-32 deterministic wallet or working with other strategies. For words that only have three letters, there is not any 4th letter. One example is https://bookmarkinglife.com/story6447200/bip39-json-bip39-generator-secrets-https-dzen-ru-bip39-phrase-com