Ever wonder whence Marcus Aurelius Antoninus, a.k.a. Caracalla, famed for his citizenship edict, a.k.a. the ‘Antonine Constitution’, got his cognomen? Enter Aurelius Victor De Caesaribus 21.2:
He was called by the name Bassianus from his maternal grandfather. But since he had brought very many garments from Gallia and had made ankle-length tunics and forced the urban population to enter dressed in such clothing for the purpose of saluting him, he was from this garment given the cognomen Caracalla.