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

https://post-wiki.win/index.php/Slot_Machine_Terms_Entering_English_Vocabulary:_A_Gamble_Worth_Taking

“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