Bip39 Checksum. The passphrase just isn't selected with the predefined list of 2048 words – it may be any word or phrase you end up picking. BIP39 specifies a list of 2048 words from which the mnemonic phrase is picked out. Every word represents a quantity in a binary sequence, https://esocialmall.com/story4433554/bip39-words-https-linktr-ee-bip39-an-unbiased-view-of-bip-39