Bip39 Standard. Entropy values must be sourced from a solid supply of randomness. This means flipping a good coin, rolling a good dice, sounds measurements and so on. Don't use phrases from guides, lyrics from tracks, your birthday or steet tackle, keyboard mashing, or nearly anything you believe is random, https://directoryorg.com/listings13092974/bip39-standard-https-linktr-ee-bip39-not-known-details-about-bip39-passphrase-generator