Bip39 Checksum. Because of the cryptographic style of BIP-39, a weak passphrase would not lessen the protection of one other wallets or enable expose the seed words. And you need to have written it down when you ended up hoping to keep an alternative open up to revive your accounts. https://socialicus.com/story4180348/bip39-generator-https-linktr-ee-bip39-the-fact-about-bip-39-that-no-one-is-suggesting