The Old Testament consists of 49 books, most of which were initially written in Jewish.
Since the Greek language, after the conquests of Alexander the Great, became the common language for almost all the nations around the Mediterranean Sea, and since in the countries that Alexander the Great had conquered were many Israelites, the Old Testament was translated in Greek (koine).
In the 3rd century B.C the translation of the Old Testament began taking place in an island called Faros (Φάρος) close to the city of Alexandria by 72 translators.
This translation is known as "Η μετάφραση των Εβδομήκοντα" = "The Translation of the seventy people".
Therefore "Η μετάφραση των Εβδομήκοντα" is the translation of the Old Testament in Koine Greek.