ClipArt ETC
"Any piece of felt; more especially, a skull-cap of felt, a hat. These seems no reason to doubt that felting is a more ancient invention than weaving, not that both of these arts came into Europe from Asia. From the Greeks, who were acquainted with this article as early as the age of Homer, the use of felt passed together with its name to the Romans. Its principal use was to make coverings of the head for the male sex, and the most common one was a simple skull-cap." — Smith, 1873

Pileus

"Any piece of felt; more especially, a skull-cap of felt, a hat. These seems no reason to doubt that…