“Double down” comes from blackjack, where you double your bet hoping your next...
https://wiki-legion.win/index.php/How_Many_Idioms_Should_I_Learn_At_Once%3F_A_Pragmatic_Guide_for_ESL_Learners
“Double down” comes from blackjack, where you double your bet hoping your next card seals the win. In English, it means to commit even more strongly to a risky choice. Common slip: learners think it means to undo a bad call—it doesn’t