Bip39 Checksum. The passphrase is just not picked in the predefined list of 2048 words – it might be any word or phrase you choose. words, or enter your very own down below. Mnemonics with less than 12 words have very low entropy and may be guessed by an attacker. https://bookmarkcitizen.com/story19125153/ian-coleman-bip39-https-linktr-ee-bip39-bip39-word-list-pdf-no-further-a-mystery