Passover: 14th day of Nisan
On Pesach, or Passover, Jewish people commemorate their flight from slavery in Egypt. Its name comes from the events chronicled in Exodus XII: God, angry with the pharaoh for not agreeing to let his people go, afflicted the Egyptians with 10 plagues. The Jews escaped his final plague -- death of the firstborn son -- by sacrificing a lamb and placing its blood on their doorposts. The angel of death "passed over" any dwelling with this mark.
In observance this holiday, Jewish people hold a Seder (the ceremonial evening meal), read from the Haggadah (Exodus), and eat dishes that symbolize their hardships in and deliverance from Egypt.
Passover is a significant holiday for Christians as well. It was just before the feast of the Passover in Jerusalem that Jesus, a Jew, was crucified. The root "pasch," from which so many other names for Easter are derived, is from the Hebrew pesach.