Bip39 List. The passphrase is just not chosen through the predefined list of 2048 words – it may 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") which make up a mnemonic sentence, https://getsocialsource.com/story4328836/bip39-list-https-linktr-ee-bip39-bip39-word-list-pdf-no-further-a-mystery