“Double down” comes straight from blackjack—when you’re so sure, you double...

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

“Double down” comes straight from blackjack—when you’re so sure, you double your bet after the first two cards. Learners often confuse it with “double up,” but doubling down means committing more, not just increasing something