Heraldry is a system of hereditary identification using visual symbols called coats of arms, or armorial bearings. In origin, armorial bearings consisted of a variety of conventional devices, or charges, displayed on the shield, or escutcheon, of the medieval knight. The practice of displaying the same emblem on the knight's surcoat, or tabard, the tunic worn over his armor, gave rise to the expression "coat of arms." The use of such symbols, which became elaborate, soon spread beyond the military field.