in Roman antiquity, was the proper folder's shoe, made in the sandal fashion, without upper leather to cover the superior part of the foot, though otherwise reaching to the middle of the leg, and fastened with thongs. The sole of the caliga was of wood, like the sabot of the French peasants, and its bottom stuck full of nails; which clavi are supposed to have been very long in the shoes of the scouts and sentinels; whence these were called by way of distinction, caligae speculatoriae; as if by mounting the wearer to a higher pitch, they gave a greater advantage to the fight; though others will have the caligae speculatoriae to have been made soft and woolly, to prevent their making a noise. From these caligae it was that the emperor Caligula took his name, as having been born in the army, and afterwards bred up in the habit of a common folder.

According to Du Cange, a sort of caligae was also worn by monks and bishops, when they celebrated mass pontifically.