The word "Apocrypha" came from the Greek word "abscondita", which means "hidden" and refers to historical writings that the Jewish rabbis did not consider inspired scripture, rather heretical writings. The Apocrypha contains around 15 books and around 12 or so of these books are accepted by the Roman Catholic Church, but all are rejected by Christians and Jews. The Roman Catholic Council of Trent decreed that the Apocrypha to be a part of the Old Testament in 1546. This decree says that anyone who rejects these books is pronounced anathema, which means excommunicated with curses.
The 15 books in the Apocrypha are the Wisdom of Solomon, Ecclesiasticus, Tobit, 1 & 2 Esdras, 1 & 2 Maccabees, Judith, Baruch, Letter of Jeremiah, Additions to Esther, Prayer of Azariah, Suzanna, Bel and the Dragon and the Prayer of Manasseh.
The Apocrypha, which also called Deuterocanonical books, should be rejected because not one of the books were written in Hebrew, nor do any of them claim inspiration and have no phrases such as "these are the words of God" or "thus saith the Lord". The Jewish church has never considered the Apocrypha to be part of sacred scripture (Romans 3:1-2). The books contained in the Apocrypha contradict the inspired scriptures. They were not allowed among the the sacred books in the first four centuries of the Christian church because they contained contradictions with themselves and the true Scriptures.
The Apocrypha teaches heretical doctrines and immoral practices, such as sinless perfection, prayers for the dead (2 Maccabees 12:43-45), interceding dead saints (2 Maccabees 15:11-14), magic (Tobit 6:4-8), Mary was born sinless (Wisdom 8:19-20), alms pay for sins (Ecclesiasticus 3:30), suicide is justified (2 Maccabees 14:42-43) , lying and assassination. In the two books of Maccabees, Antiochus Epiphanes is made to die three different ways in three different places
The Lord Jesus Christ and the Apostles never quoted the Apocrypha like they did the Old Testament. Jesus reveals the three division of the Old Testament in Luke 24:44 as the Law of Moses, the Prophets and Psalms with the Apocrypha not being mentioned.
Those are just some of the various reasons that the King James translators rejected the Apocrypha and put it in the middle of the Testaments, showing that they were not inspired scripture, rather just historical writings filled with errors.
Like Josephus(37-95 A.D.), who was a Jewish historian, I also believe that the Apocrypha books were not wrote by prophets, rather "slipped in" and not a part of sacred scripture. Therefore the King James translators were correct by omitting the Apocrypha from the Old Testament. Unlike the Masoretic text that the King James translators used, the Vaticanus and Sinaiticus include the Apocrypha in the Old Testament. Both, the Vaticanus and Sinaticus are the foundation for the corrupt new version bibles.