"Double down" comes from blackjack—when you double your bet after seeing your...

https://andersonssuperbthoughtss.timeforchangecounselling.com/why-english-business-language-uses-card-game-terms

"Double down" comes from blackjack—when you double your bet after seeing your first two cards, betting you’re onto a winner. Language learners often overuse it, thinking it means just 'try harder.' Nope, it’s about risk, not effort