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

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

“Double down” comes straight from blackjack: when you’re confident, you double your bet with just one extra card. Language learners often use it to mean “repeat something” instead of “take a bigger risk