Heraldry exists because medieval knights in full armor all looked identical — painting symbols on shields was literally a matter of life and death.
The system of designing, displaying, and regulating coats of arms and other armorial bearings; the study and classification of such symbols.
From Anglo-Norman heraldrie, from heraud (herald), from Frankish *hariwald (army commander), from Proto-Germanic *harjaz (army) + *waldaz (ruler, power). The practice of hereditary identification through symbols on shields emerged in the 12th century. Key roots: *harjaz (Proto-Germanic: "army, host, war band"), *waldaz (Proto-Germanic: "ruler, power, authority").
Heraldry emerged not from vanity but from a genuine battlefield problem: once knights encased themselves in full armor with closed helmets, nobody could tell friend from foe. Distinctive symbols painted on shields became a matter of life and death. The word herald itself means "army commander