“Double down” comes straight from blackjack—when you double your bet after...
https://dlf-ne.org/is-up-the-ante-a-gambling-term-unpacking-a-classic-business-idiom/
“Double down” comes straight from blackjack—when you double your bet after seeing your first two cards, hoping to hit the jackpot. Learners often misuse it as ‘double up,’ which sounds like doubling a quantity but misses the strategic risk-taking angle