“Double down” comes from blackjack: when you’re confident, you double your...

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

“Double down” comes from blackjack: when you’re confident, you double your original bet for a single extra card. Learners often misuse it to mean ‘try harder’ in any context—nope! It’s about risk and commitment, not just effort