If you are interested in the true history of the Septuagint you can go to this link:
http://www.studylight.org/enc/isb/view.cgi?number=T7825
The Septuagint's main value, prior to the discovery and translation of the Dead Sea Scrolls is that it was a direct translation of the Hebrew text from manuscripts that were written around 950 BC. Because of this they represented the oldest Hebrew manuscripts available until the Dead Sea Scrolls were discovered. Now, the accuracy of the Septuagint has been confirmed by comparison to the texts available from the Dead Sea caves.
Another equally important value of the Septuagint is that it was commissioned by the Library at Alexandria in Egypt to be as accurate grammatically as possible a Greek translation of the Hebrew Scriptures. It was a translation performed by 70 of the top Hebrew and Greek scholars that were available at the time.
Because of this we can see how many of the Hebrew terms which are difficult to translate related to their equivalent meaning in the Greek language which was much more expressive in understanding and explaining theological concepts.
Since the Septuagint was accomplished long before the life of Origen who lived from 185-254 AD he had nothing to do with it's development. the only thing that they had in common is that both had their roots in Alexandria. While it is true that Origen was influential in Alexandria, and had quite a few theological problems, since his problems were based in Gnosticism and an allegorical view of Scripture he didn't need to try and re-write Scripture to say what he wanted it to say. He just interpreted Scripture however he wanted no matter what it really said. Just like many of the false teachers today.
As to the original post. The language used in Israel at the time of Christ was Aramaic which was a derivation from Hebrew brought on by the extended exile in Babylon. Only the very educated in Israel were able to read Hebrew. Mainly, the Scribes, which was why they were the Copyists of the Hebrew manuscripts, as well as the interpreters of the Law. Koine Greek was the trade language of the Roman Empire and most Jews were able to communicate in Koine Greek, at least enough to get by. Similar to many people in other countries today being able to speak some English in order to accomodate un-educated American travelers abroad.