Bip39 Mnemonic. The passphrase is not chosen through the predefined list of 2048 words – it can be any word or phrase you choose. BIP39 is really a design implementation that lays out how copyright wallets produce the list of words (or "mnemonic codes") which make up a mnemonic sentence, https://wildbookmarks.com/story19243412/bip39-passphrase-https-linktr-ee-bip39-getting-my-ian-coleman-bip39-to-work