"Double down" comes straight from blackjack: you double your initial bet after...

https://scarlettsultimatethoughtss.iamarrows.com/gambling-idioms-in-business-english-a-risk-idioms-list-you-should-know

"Double down" comes straight from blackjack: you double your initial bet after seeing your first two cards, hoping for a strong third. Language learners often misuse it to mean “try harder,” but it specifically means committing more with risk