In Paul’s extended metaphor, God’s special olive tree represents the people of God. This image would have been familiar to his readers. The olive tree was the most common fruit tree in the Mediterranean region. It was also already used as a symbol for Israel in the Old Testament (Jeremiah 11:16; Hosea 14:5–6).
Paul describes non-Jewish (gentile) Christians as branches from a wild olive tree because they were not originally part of God's people.