“Double down” comes from blackjack, when 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, when you double your bet after seeing your first two cards, betting on a strong hand. Learners often misuse it to mean “try harder” in any situation—nope, it’s about risk, not effort