The "shame, shame" hand gesture

[Milossarian]

You know the one, where you seem to imitate peeling a carrot with your index fingers.

What is its origin? What is it supposed to represent?

[Johnny L.A.]

The pointing gesture is to draw attention to the wrong-doer. "Look at him! Look what he did!" And the motion of striking or stroking the finger is to symbolize corporal punishment.