“Double down” comes straight from blackjack: you double your bet when you’re...

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

“Double down” comes straight from blackjack: you double your bet when you’re confident your hand will win. Language learners often misuse it thinking it means "do something twice," but it’s about increasing commitment, not repetition