“Double down” comes from blackjack: when you’re confident, you double your...

https://camilassplendidblogs.raidersfanteamshop.com/play-your-cards-close-to-your-chest-origin-usage-and-esl-pitfalls

“Double down” comes from blackjack: when you’re confident, you double your original bet for a single extra card. Learners often misuse it to mean ‘try harder’ in any context—nope! It’s about risk and commitment, not just effort