But for his mighty deeds, he was subsequently called Karna. Because the greatly illustrious hero removed his natural coat of Arms (from his breast).
ततो वैकर्तनः कर्णः कर्मणा तेन सोऽभवत्। आमुक्तकवचो वीरो यस्तु जज्ञे महायशाः॥