Thankfully, in 2012 the developer Pieter Wuille established the BIP32 specification at The bottom with the hierarchical deterministic wallets. Collectively with it, Pieter made a mathematical function to make a learn key from which to derive all other keys inside of a deterministic way. This post explains BIP39, the standard https://captainbookmark.com/story18758495/bip39-phrase-generator-can-be-fun-for-anyone