“Double down” comes from blackjack: you double your bet when confident in your...

https://idiominsider.com/talking-odds-at-work-the-risk-idioms-every-english-learner-gets-slightly-wrong/

“Double down” comes from blackjack: you double your bet when confident in your hand, doubling risk and reward. Learners often think it means simply “try harder,” but it’s about upping the stakes, not just effort