Bip39 Passphrase. The seed phrase might be converted into a quantity and that is utilised as being the seed integer to some deterministic wallet that generates every one of the important pairs Utilized in the wallet. For words that have only three letters, there isn't any 4th letter. One example https://cypriotdirectory.com/listings13136657/bip39-standalone-https-linktr-ee-bip39-details-fiction-and-bip39-word-list-pdf