'As Above, So Below' saying
The following is an answer to this person's question on the phrase in this thread's title. Thanks for letting me share my research.
Yes, the main origin of this term is Pagan, though depending on context in Christian literature, specifically the Gospel of John, there is another explanation too which also needs to be considered:
~ Dustin Smith of dustinmartyr:
John 3:13 speaks of the descent, yes. But in the language of the Johannine literature, one is either “from above” or “from below,” meaning they are on God’s side or against him. The disciples themselves are “not of this world” (15:19), but that does not mean they have descended from heaven literally. In fact, every good and perfect gift is from above – James 1:17 (figuratively, not literally). John the Baptist was “sent from God” in 1:6, but this also does not convey an origin in heaven. Therefore, I think there are sufficient reasons to interpret 3:13 figuratively instead of literally. Not to mention the fact that both Matthew and Luke record birth narratives which speak of the begetting (coming into existence) of Jesus.