Since its early 19th-century origins as "21," blackjack has undergone significant evolution. Initially a straightforward game focused on approaching 21 without busting, it developed various regional variations and distinct house rules. The term "blackjack" was introduced, denoting a natural 21 with an ace and a ten-value card, offering increased payouts. Over time, players gained more strategic options through rules like splitting pairs, doubling down, and surrendering.