“Double down” means you’re betting twice as much because you’re...
https://spark-wiki.win/index.php/What_Does_Volatility_Mean_in_Casino_Slots%3F_A_Language_Lover%E2%80%99s_Take
“Double down” means you’re betting twice as much because you’re confident—straight from blackjack, where you double your wager after seeing your first two cards