In the final verse of the first reading God told the people that the Passover was to be a perpetual institution. Thirteen hundred years later Jesus celebrated the Passover with his disciples. And at that same night, he transformed the Passover into our Mass, so that at each Mass we celebrate the Passover.
Oddly, from the start the word Passover was applied in two distinct ways. In the first way, in verses ten and eleven of Exodus, Chapter Twelve, it described the Lord leading the people in passing over from slavery to the road to freedom, and ultimately into the Promised Land.
Then, in the next verse, verse thirteen, the name Passover is applied to death passing over those who are marked with the blood of the lamb.
Both those meanings of Passover are retained in the Mass. First, in the Mass we make a departure from sinfulness, letting Jesus lead us to the Promised Land. Then, secondly, his blood forces death to pass over, not harming us.