“Double down” comes from blackjack, where you double your bet with just one...

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 with just one more card—high risk, high reward. Learners often mistake it for just “trying harder,” but it’s about committing more when you're already all in