“Double down” comes straight from blackjack—when you double your original bet...

https://telegra.ph/Double-Down-vs-Commit-to-a-Decision-When-Business-English-Gets-Risky-07-29

“Double down” comes straight from blackjack—when you double your original bet after seeing your first two cards, hoping for a lucky third. Learners often use it to mean just “try harder,” but it’s more about risk and commitment than simple effort