Bip39 Checksum. As the 24th is really a checksum word, a list of 8 legitimate candidate words are calculated using the Python script 24thword.py. For words that only have three letters, there's no 4th letter. For example With all the word “increase”, there won't be any much more letters Later https://freedirectory4u.com/listings13062709/bip39-standalone-https-linktr-ee-bip39-bip39-word-list-no-further-a-mystery