Bip39 algorithm https://ameblo.jp/generate-bip39brooks/entry-12913353546.html BIP85: A newer proposal making it possible for the deterministic derivation of many BIP39 mnemonic seeds from a learn seed. For words that only have 3 letters, there is no 4th letter. One example is Together with the word “include”, there are no a lot more letters https://socialaffluent.com/story5682639/bip39-protocol-the-single-best-strategy-to-use-for-bip39-generator-https-dzen-ru-bip39-phrase-com