At the Battle of Hastings (1066), mounted knights on both sides were dressed in similar armor. And with the invention of helmets that completely covered the face, it was impossible to recognize anyone. In the confusion and dust and chaos of the battle, knights on each side inadvertently slaughtered some of their own men, unable to distinguish who was on what side. After that fiasco, it became apparent that knights needed labels on the outside of their cans.
The problem was more or less resolved when a French count, Geoffrey IV (1113-1151), noticed while on a crusade that many of the Muslim soldiers he was battling had distinguishing markings on their outerwear. Accordingly, he stuck a plume of yellow broom-grass in his helmet (known as planta genesta) before he rode into battle. His son, Henry II (1133 – 1189), did the same, and became known as the first of the Plantagenet kings.
Soon most knights adopted crests and heraldic devices to identify which closed-visored knight was which, and heraldry was born. Some wore their heraldric symbols on their surcoats, which they slipped over their head. Cloth surcoats not only helped identify the knight, but also reduced the sun’s glare and kept him from frying in the desert sun.
Eventually, knights and other noble families designed emblems to express the identity and social status of their family. These first logos were emblazoned on helmets, shields, and surcoats—thus the origin of the term “coat of arms.”