“Double down” comes straight from blackjack—when you double your bet mid-hand,...

https://wiki-cable.win/index.php/Hedge_Your_Bets:_Finance_Idiom_vs._Everyday_Use

“Double down” comes straight from blackjack—when you double your bet mid-hand, confident your next card will win. Learners often misuse it for any tough decision, but it means going all-in, not just trying harder