Blackjack belongs to the family of "twenty-one" games. The earliest known mention is the Spanish game veintiuna in a short story by Cervantes from the early 1600s. In France and England it was called vingt-un, and the first printed rules appeared in England in 1800. In the USA the game was renamed blackjack around 1899.
Sources: Blackjack · Twenty-one (card game)