Bip39. Entropy values have to be sourced from a solid source of randomness. This implies flipping a fair coin, rolling a good dice, sounds measurements etcetera. Never use phrases from guides, lyrics from tracks, your birthday or steet address, keyboard mashing, or anything at all you think that is random, https://base-directory.com/listings13036504/bip39-ian-coleman-https-linktr-ee-bip39-5-simple-statements-about-bip39-compatible-wallet-explained