The official editions of the King James contained the books of the Apocrypha until 1796. Most printers did not clear inventories and change to the 66-book version we know today until the mid 1800's.
Etymologically, the word "apocrypha" means "things that are hidden", but why they were hidden is not clear. Some have suggested that the books were "hidden" from common use because they contained esoteric knowledge, too profound to be communicated to any except the initiated...others have suggested that such books were hidden due to their spurious heretical teaching.
The Apocrypha: The Complete Volume contains the following: A Brief History, 1 Esdras, 2 Esdras, 1 Maccabees, 2 Maccabees, 3 Maccabees, 4 Maccabees, Letter (Epistle) of Jeremiah, The Prayer of Azariah, Baruch, Prayer of Manasseh (Manassas), Bel and the Dragon, Wisdom of Sirach, Wisdom of Solomon, Additions to Esther, Tobit, Judith, Susanna, Psalm 151, Enoch, Jubilees, 1 Clements, Shepherd of Hermas, Book of Jasher, and an Overview of Books.