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

https://dlf-ne.org/is-up-the-ante-a-gambling-term-unpacking-a-classic-business-idiom/

"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