An ancient tradition says that 70 Jewish scholars were in a different room when they translated the Torah from Hebrew into Greek, yet they all wrote down exactly the same text. People thought this was a miracle. The Latin language word for "70" is "septuaginta", and the word "Septuagint" comes from that. Another way to write "70" is "LXX" which is why writers sometimes use that as a short name for Septuagint.