“Double down” comes straight from blackjack: you double your original 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 original bet after seeing your first two cards, hoping for a strong hand. Language learners often misuse it to mean just “try harder,” but it’s about risk—doubling stakes, not effort.