“Double down” comes from blackjack, where you double your bet on a strong hand...

https://dlf-ne.org/is-up-the-ante-a-gambling-term-unpacking-a-classic-business-idiom/

“Double down” comes from blackjack, where you double your bet on a strong hand to boost winnings. Language quirk: learners often think it means playing it safe, when it actually means taking a bigger risk. Use it when you’re all in, not cautious.