BIP39 stands for Bitcoin Improvement Proposal 39. The words are picked from a certain list of 2048 prevalent English words which can be used to the generate a binary seed (your private critical). Standard recovery phrases use a selected list of 2048 words pursuing the BIP39 standard (Bitcoin Enhancement Proposal https://thefairlist.com/story9573061/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator