“Double down” hails from blackjack—doubling your bet after seeing your cards,...

https://dlf-ne.org/is-up-the-ante-a-gambling-term-unpacking-a-classic-business-idiom/

“Double down” hails from blackjack—doubling your bet after seeing your cards, betting on a better hand. Learners often misuse it to mean simply “try harder,” missing the risk-and-reward edge