From The Art and Popular Culture Encyclopedia
Sacrifice (from a Middle English verb meaning "to make sacred", from Old French, from Latin sacrificium: sacer, "sacred" + facere, "to make") is commonly known as the practice of offering food or the lives of animals or people to the gods as an act of propitiation or worship. The term is also used metaphorically to describe selfless good deeds for others or a short term loss in return for a greater gain (such as in a game of chess).
The practice of sacrifice is found in the oldest human records. The archaeological record contains human and animal corpses with sacrificial marks long before any written records of the practice. Sacrifices are a common theme in most religions, though the frequency of animal, and especially human, sacrifices are rare today.