Bip39 bitcoin core https://jaspermuxp089.yousher.com/top-5-online-bip39-generators-for-effortless-copyright-security Abra - A cellular wallet that supports BIP39 seed phrases, giving both of those wallet and exchange features for cryptocurrencies. For words that have only 3 letters, there isn't a 4th letter. Such as Along with the word “increase”, there are no more letters Later on https://bookmarkchamp.com/story19934177/bip39-meaning-bip39-npm-no-further-a-mystery-https-dzen-ru-bip39-phrase-com