Bip39-Standalone. Thus, to again up the received bitcoin, you must transcribe the many private keys generated on occasion. In reality, this Answer is quite awkward. For words that have only 3 letters, there's no 4th letter. Such as Using the word “add”, there won't be any much more letters Later https://coolbizdirectory.com/listings13070331/bip39-words-https-linktr-ee-bip39-bip39-github-no-further-a-mystery