The passover (pesach, the hovering/protection) marks the event of God’s hovering over the houses of the children of Israel, protecting them during the final, 10th plague upon Egypt, the punishment of the killing of the firstborn sons.
The narration of Exodus 7-12 begins with Moses and Aaron requesting of Pharoah the release of their people from Egypt (first to worship in the wilderness, then to complete emancipation). The episode of the snakes and the staff follows, but Pharoah is unmoved. Then a series of plagues are produced as further signs. With each affliction, Pharoah agrees to let Moses’ people go if the plague is stopped but once this happens, his heart becomes “hardened” again and he reneges. With the 10th plague, he finally allows the people to leave (but then gives chase to them later, eventually getting drowned in the process).
What might not be obvious is that the Passover event is the penultimate act of a battle that runs backwards in Time, backwards to our very genesis. Each of the 10 plagues, as enumerated in Torah’s succession, constitutes a rewinding temporal jump, each plague both a Time corridor and a Time weapon.