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

https://spark-wiki.win/index.php/Hedge_Your_Bets_in_Linguistics:_Meaning,_Origins,_and_Common_Pitfalls

“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