Caligula. The nickname derives from the caliga, the typical Roman military shoe
Gaius Julius Caesar Augustus Germanic (12-41 AD), son of Germanicus, one of the most valiant and beloved leaders of Ancient Rome (see https://www.pilloledistoria.it/4060/storia-antica/lamatissimo-germanico) ruling with the name of Gaius Caesar , went down in history as Caligula, but why?
The caligas they were sturdy military sandals worn by soldiers; the thick leather sole reinforced by wide and pointed nails ensured a perfect grip even on the most difficult terrain, while the leather strips, which fastened around the foot and ankle, kept them well adherent to the leg and allowed the fingers could remain uncovered, in order to avoid problems due to the rubbing of the leather on the skin during marches.
You may be wondering what all this has to do with the Emperor ...
Well, since Germanicus used to take his still young son with him in military campaigns, it ended up that Gaius Caesar became almost a sort of mascot loved and fondled by his subordinates, who nicknamed the child "caligula", or “ little caliga “.
In short, a bit like calling it "shoe", a decidedly tender, sweet and absolutely jarring nickname with what became the personality of the interested party once he became an adult, a man who looked nothing like his heroic father and so crazy and bloodthirsty that he was counted as one of the worst emperors of the city (see https://www.pilloledistoria.it/9757/storia-antica/caligola-lo-schizofrenico, https://www.pilloledistoria.it/8853/storia-antica/dal-cibo-al-cavallo-alcune- follie-caligola and https://www.pilloledistoria.it/8853/storia-antica/dal-cibo-al-cavallo-alcune-follie-caligola).