“Double down” comes from blackjack—a bold move where you double your bet after...

https://xeon-wiki.win/index.php/Idioms_That_Sound_Negative_but_Are_Actually_Neutral

“Double down” comes from blackjack—a bold move where you double your bet after seeing your first cards, betting on a strong hand. Learners often mistake it for just trying harder, but it’s really about raising the stakes, not just effort