caligula

cognomen of the third Roman emperor (12 C.E.-41 C.E.), born Gaius Caesar. The nickname is Latin, literally “little boot,” given when he joined his father on military campaigns when still a toddler, in full, child-sized military gear; diminutive of caliga “heavy military shoe,” of unknown origin.

A cruel and insane ruler of the Roman Empire in the first century a.d.; one of the twelve Caesars. To humiliate the senators of Rome, he appointed his horse to the senate.