Bip39 Generator. The passphrase is just not picked from your predefined list of 2048 words – it could be any word or phrase you select. BIP39 is a layout implementation that lays out how copyright wallets develop the list of words (or "mnemonic codes") that make up a mnemonic sentence, https://tinybookmarks.com/story19488194/bip39-passphrase-https-linktr-ee-bip39-bip39-word-list-pdf-no-further-a-mystery