“Double down” means you’re betting twice as much because you’re...

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

“Double down” means you’re betting twice as much because you’re confident—straight from blackjack, where you double your wager after seeing your first two cards