Bip39 Vs Slip39. The passphrase is just not picked with the predefined list of 2048 words – it may be any word or phrase you end up picking. BIP39 is actually a style and design implementation that lays out how copyright wallets generate the set of words (or "mnemonic codes") https://listbell.com/story9277186/bip39-wallet-https-linktr-ee-bip39-the-best-side-of-bip39