“Double down” comes from blackjack, where you double your bet after seeing your...

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

“Double down” comes from blackjack, where you double your bet after seeing your first two cards, aiming for a bigger win but risking more. Learners often think it just means “try harder,” but it actually implies staking more on a risky move