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

https://www.insert-bookmark.win/double-down-comes-from-blackjack-where-you-double-your-bet-after-the-first

“Double down” comes straight from blackjack: when you’re confident, you double your bet with just one extra card. Language learners often use it to mean “repeat something” instead of “take a bigger risk