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

https://mill-wiki.win/index.php/Blue_Chip_Companies:_Meaning,_History,_and_Their_Gambling_Origins

“Double down” comes straight from blackjack: when you’re confident, you double your bet and hope for a good card. Learners often mess this up, thinking it means just “try harder” in any situation. Nope—it’s about backing your bet, not vague effort