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

https://penelopesnewchat.yousher.com/how-to-use-idioms-without-sounding-like-a-textbook

“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