“Double down” comes from blackjack, where you double your bet on a strong hand...
https://milasultimatejournal.theglensecret.com/hedge-your-bets-finance-idiom-vs-everyday-use
“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.