Originally the term meant the ancient Greek Old Testament. The term is derived from the Latin word septuaginta (seventy) and is based on the legend that is given in the Letter of *Aristeas according to which the Greek translation of the Hebrew Pentateuch was a work of 70 (or rather 72) translators. The term Septuagint was then extended to include the Greek translation of all other books of the Hebrew and Aramaic Old Testament and even the books originally written in Greek. Together with the Greek books of the New Testament the Septuagint is still the official Bible of the Greek Orthodox and the Catholic Church of the *Greek rite. A.G.H.
Source: (Septuagint, L.F. Hartman) 34.