Blackjack is thought to have originated from Spain in the 1500’s.  At that time it was simply known as Twenty One (or Veintiuna).  In much of Europe in retained the name, with also the name Pontoon proving popular.   Twenty One was introduced into the casinos in the United States, and to encourage action and add an extra appealing element to the game As Js and As Jc each received a large bonus (The Blackjack Bonus).  Over time this name become a more popular way to refer to Twenty One, and eventually the specific bonus was shifted to any ace and any ten, with the size of the bonus naturally being reduced.