having just looked up Septuagint. Our pastor was telling us about it last night at Bible Study, and when I asked if it was based on something about seven, he said no!

Well, not sure what he meant by "no". Latin septuaginta '70' is definitely realted historically to septem '7'. The name for the Koine Greek translation of the Tanakh (Old Testament) comes from a passage in the Talmud that says that 72 men translated the Torah (Pentateuch, first five books of the Old Testament) from Hebrew into Greek.

Ceci n'est pas un seing.