The original title of the Septuagint in ancient Greek was Ἡ μετάφρασις τῶν Ἑβδομήκοντα, which then comes to the Latin phrase versio septuaginta interpretum and finally shortened to "Septuagint". The term Septuagint is first found during the time of Saint Augustine of Hippo when he refers to it as the Septuaginta. Commonly, the Church utilizes either the letter G or the Roman numeral LXX. Written in Koine Greek, some sections contain Semiticisms (idioms and phrases based on Hebrew and Aramaic - hence Semetic) while other sections have a much more intense and stronger Greek influence (Daniel and Proverbs specifically).
The legend of the Septuagint's creation
Ptolemy II Philadelphus, the Greek King of Egypt gathered together seventy-two Jewish Scholars in an effort to translate the Torah from Hebrew to koine Greek for preservation within the Library of Alexandria. In the Tractate Megillah of the Babylonian Talmud we can find an account of this request:
King Ptolemy once gathered 72 Elders. He placed them in 72 chambers, each of them in a separate one, without revealing to them why they were summoned. He entered each one's room and said: "Write for me the Torah of Moshe, your teacher". God put it in the heart of each one to translate identically as all the others did.
Philo of Alexandria expanded on this original story, writing that the number of scholars chosen by Ptolemy II was based on choosing six scholars from each of the twelve tribes of Israel. The finished translations were delivered to Ptolemy two days before the Tenth of Tevet (עשרה בטבת - a morning to evening minor fast to mourn the siege of Jerusalem by Nebuchadnezzar II of Babylon , in 2020 this will fall on December 25th and in 2019 it fell on January 7th).
Differences between the Septuagint and the Hebrew Texts
The Tanakh (Hebrew Bible) has three sections - Torah (Law), Nevi'im (Prophets), and Ketuvim (writings) were as the Septuagint was divided into four sections - law, history, poetry and prophets. The Masoretic texts separated some of the books that got grouped together in the Septuagint - the books of Samuel and Kings are consolidated into a single four-part book entitled Βασιλειῶν (Of Reigns) which is supplemented by the combining the Chronicles books as Παραλειπομένων (Of Things Left Out).
Another difference between the two are the inclusions of the so called Deuterocanonical or apocryphal books. These are books found in the Septuagint but not the Hebrew texts - the book of Tobit, Judith, the Wisdom of Solomon, Sirach, Epistle of Jeremiah (which eventually become the sixth chapter of Baruch in the Vulgate), additions to Daniel, additions to Esther, 1, 2, 3, and 4 Maccabees, 1 Esdras, Odes, the Psalms of Solomon and Psalm 151.
Greek name Transliteration English name
Προσευχὴ Μανασσῆ Proseuchē Manassē Prayer of Manasseh
Ἔσδρας Αʹ 1 Esdras 1 Esdras or 1 Ezra
Τωβίτ Tōbit Tobit
Ἰουδίθ Ioudith Judith
Ἐσθήρ Esthēr Esther
Μακκαβαίων Αʹ 1 Makkabaiōn 1 Maccabees
Μακκαβαίων Βʹ 2 Makkabaiōn 2 Maccabees
Μακκαβαίων Γʹ 3 Makkabaiōn 3 Maccabees
Μακκαβαίων Δ' Παράρτημα 4 Makkabaiōn Parartēma 4 Maccabees
Ψαλμός ΡΝΑʹ Psalmos 151 Psalm 151
Σοφία Σαλoμῶντος Sophia Salomōntos Wisdom or Wisdom of Solomon
Σοφία Ἰησοῦ Σειράχ Sophia Iēsou Seirach Sirach or Wisdom of Sirach
Βαρούχ Barouch Baruch
Ἐπιστολὴ Ἰερεμίου Epistolē Ieremiou Epistle or Letter of Jeremiah
Δανιήλ Daniēl Daniel (with additions)
Ψαλμοί Σαλoμῶντος Psalmoi Salomōntos Psalms of Solomon
Several copies of the Septuagint were found among the Dead Sea Scrolls (kept by a sect of Jews called the Essenes) and the pre-Christian Jewish scholars Philo and Josephus considered the Septuagint equal to the original Hebrew texts. As Christianity grew in popularity, the Jewish scholars began viewing the association of the Septuagint with gentile Christians (as early Christians used the Septuagint out of necessity - most were Greek speakers and could not read Hebrew). Thus Jewish scholars began relying on Hebrew or Aramaic Targum manuscripts compiled later by the Masoretes.
The early Christians were so dependent on the Septuagint because Greek was the lingua franca of the Roman Empire. The early church used the fact the Septuagint was translated well before the arrival as Jesus as evidence that it was the most accurate and that it lends to a more Christological interpretation than send century Hebrew texts. For example, Saint Irenaeus writes that Isaiah 7:14 in the Septuagint that a virgin (παρθένος or bethulah in Hebrew) would conceive where as the Ebionites used the phrasing "young woman" in later translations.
Saint Jerome would much later break with early Church tradition and translate the Old Testament of his Vulgate from Hebrew rather than the Greek found in the Septuagint. Saint Augustine sharply criticized this move, accusing it of heresy. Eventually though, Saint Jerome's version grew more popular and displaced most of the Septuagint's Old Latin translations. The Eastern Orthodox Church uses the Septuagint as the basis for their translations of the Old Testaments and uses the untranslated Septuagint for the Greek portions of the liturgical language.