The scapegoat was a goat used in a special ceremony on the Day of Atonement. During this important religious day, the high priest would symbolically place the sins of all the Israelite people on this goat. Then the goat would be sent away into the wilderness, symbolically carrying away the people's sins (Leviticus 16).
Scapegoat
From Tyndale Bible Dictionary, adapted by Mission Mutual. CC BY-SA 4.0.