“Double down” comes from blackjack, where you double your bet after seeing your...

https://wiki-dale.win/index.php/Hedge_Your_Bets_Meaning:_Finance_vs_Everyday

“Double down” comes from blackjack, where you double your bet after seeing your first two cards, aiming for a big win on one more. Learners often mess it up by thinking it means “back off” or play safe—it’s the opposite: you’re going all in