For words that only have 3 letters, there is no 4th letter. By way of example with the word “incorporate”, there won't be any a lot more letters afterwards and so needs to be the word "insert". The word “addict” is during the BIP39 wordlist however, you might have utilized https://bookmarklogin.com/story19104875/bip39-phrase-generator-can-be-fun-for-anyone