The first written reference is to be found in a book of Miguel de Cervantes, the author of Don Quixote -and a gambler himself-. The main characters of his tale "Rinconete y Cortadillo", from "Novelas Ejemplares", are a couple of cheaters working in Seville. They are proficient at cheating at "veintiuna" (Spanish for twenty-one), and stated that the object of the game is to reach 21 points without busting and that the Ace values 1 or 11.

The game is played with the spanish deck, that is without tens, which makes the game similar to the current spanish 21. This short story was written between 1601 and 1602, so the game was played in Castilia since the beginning of the 17th Century or even earlier. Later references of this game are to be found in France and Spain.

 

When 21 was first introduced in the United States it was not very popular, so gambling houses tried offering various bonus payouts to get the players to the tables. One such bonus was a 10-to-1 payout if the player's hand consisted of the ace of spades and a black Jack. This hand was called a "blackjack" and the name stuck to the game even though the bonus payout was soon abolished. As the game is currently played, a "blackjack" may not necessarily contain a jack or any black cards at all.