From pasach ("to pass over, to spare"), pesach denotes both the annual feast commemorating Israel's deliverance from Egypt and the lamb slaughtered on its eve. The blood of the pesach lamb on the doorposts caused the angel of death to "pass over" Israelite households on the night God struck Egypt's firstborn (Exodus 12). The feast was thereafter observed on the 14th of Nisan as the foundational celebration of redemption.
The Passover is the interpretive lens of all biblical redemption. Every element — the unblemished lamb, the blood applied to doorposts, the haste of departure, the bitter herbs of slavery — finds its ultimate fulfillment in Jesus Christ. Paul declares explicitly: "Christ, our Passover lamb, has been sacrificed" (1 Corinthians 5:7). The Lord's Supper is the new covenant Passover meal, where believers proclaim the Lord's death until He comes (1 Corinthians 11:26).