Bip39 Tool. The passphrase just isn't picked from your predefined list of 2048 words – it might be any word or phrase you select. BIP39 is actually a style implementation that lays out how copyright wallets make the set of words (or "mnemonic codes") which make up a mnemonic sentence, https://checkbookmarks.com/story5214289/bip39-https-linktr-ee-bip39-5-essential-elements-for-bip39-word-list