During the 17th century and well into the 18th century, the Spanish dollar was the currency used in the American colonies. In order to make the change, it was decided that the dollar could be divided into eight equal pieces.
In Chapter 10 of Robert Louis Stevenson’s “Treasure Island” we learn that Long John Silver’s parrot, Cap’n Flint is well acquainted with the phrase: “And the parrot would say, with great rapidity, “Pieces of eight! Pieces of eight! Pieces of eight!” till you wondered that it was not out of breath, or till John threw his handkerchief over the cage.”
Historically Speaking 