E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A Greek version of the Old Testament, so called because it was made, in round numbers, by seventy Jews; more correctly speaking, by seventy-two. Dr. Campbell disapproves of this derivation, and says it was so called because it was sanctioned and authorised by the Jewish Sanhedrim or great council, which consisted of seventy members besides the high priest. This derivation falls in better with the modern notion that the version was made at different times by different translators between B.C. 270 and 130. (Latin, septuaginta, seventy.)
The Septuagint contains the Apocrypha. According to legend, the Septuagint was made at Alexandria by seventy-two Jews in seventy-two days.