Chaperon was a form of hood or, later, highly versatile hat worn in all parts of Western Europe in the Middle Ages. Initially a utilitarian garment, it first grew a long partly decorative tail behind called a liripipe, and then developed into a complex, versatile and expensive headgear after what was originally the vertical opening for the face began to be used as a horizontal opening for the head. It was especially fashionable in mid-15th century Burgundy, before gradually falling out of fashion in the late 15th century and returning to its utilitarian status. It is the most commonly worn male headgear in Early Netherlandish painting, but its complicated construction is often misunderstood. (source)