In the context of high medieval military equipment, the coif typically refers to the 'coif of mail' (hauberk-hood), a vital component of the knightly panoply from the 11th through the 14th centuries. Constructed from interlinked iron rings, it was designed to protect the skull, ears, and neck, often featuring a 'ventail' or flap of mail that could be drawn across the mouth and chin for additional facial defense. While originally an integrated extension of the hauberk, it evolved into a separate garment by the 13th century, often worn over a padded 'armouring cap' to absorb kinetic impact.
Beyond the field of battle, the term also identifies the white linen or silk skullcaps worn by English Serjeants-at-Law, representing one of the highest orders of the legal profession. In this civil and heraldic capacity, the coif symbolized legal authority and was frequently depicted in tomb effigies of the judiciary. In heraldry, while less common than the helmet, a head depicted with a coif may appear in crests or as a charge, denoting either a specific military rank or legal status depending on the tincture and form.