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

https://www.4shared.com/office/12SjSzBTge/pdf-11845-28864.html

“Double down” comes straight from blackjack: when you’re confident, you double your bet and hope for a lucky card. Learners often misuse it as just “doubling effort,” but it’s about risk—betting more when the stakes look good, not simply trying harder.