By nature, we may be said to be outcasts. We're cast out with our first parents from the Garden of Eden, cast out from the presence of God, banished, driven out, and the Lord in his work in salvation is bringing in those outcasts. He's gathering a people together. But then it also applies to those that are outcasts because of what God does for them in a call by grace. The Apostle Paul says that I am crucified unto the world and the world is crucified unto me. In other words, the world did not want him and he did not want the world. When the Lord works in a sinner's heart, then those that may have been their worldly friends, they don't want them anymore. Their names are cast out as an outcast.