The Linen Coif is cap that was worn in the medieval period, simple piece of linen formed from a couple panels of fabric tied around the head.
About as basic a cap as you can get.
I also like to think of it as head underwear since it also protects a more expensive hat from coming into contact with your greasy, filthy, flea infested, medieval hair.
Coifs come in many forms, padded for wearing under helmets, chainmail coifs are a form of armour and coifs also became garment worn after the medieval period by nuns.
