Καλλιγόλας

Thus did they used to call Gaius, the emperor of the Romans, since from early boyhood he grew up spending most of his time in the military camps and would wear soldiers' shoes. So from the "caligae"¹ they named him Caligula.²
Or Gaius [was called] Caligula on account of his birth in the military camps; so says Aelian in his work On Divine Influences.³