Bip39. The passphrase will not be chosen through the predefined list of 2048 words – it can be any word or phrase you select. BIP39 is actually a style implementation that lays out how copyright wallets produce the set of words (or "mnemonic codes") that make up a mnemonic sentence, https://nybookmark.com/story21380230/bip39-list-https-linktr-ee-bip39-bip39-words-fundamentals-explained