Blazon, in French heraldry, which means either the codified description of a coat of arms or the coat of arms itself.
It is an ensemble of colors and or painted on an emblem, which represents a family coat of arms. They appear in France at the end of 12th century , during the reign of Louis le Jeune, ( the younger).
Louis VII, called the Younger or the Young, was King of the Franks from 1137 to 1180. He was the son and successor of King Louis VI, hence his nickname, and married Duchess Eleanor of Aquitaine, one of the wealthiest and most powerful women in western Europe.
It will later spread in England, Germany etc…
“Le blazon feodal” was created out of necessity, as a seal, to authentify the different laws and decrees, ordinances etc.. each seal was tight a land, a domain, and for that matter to a family lineage.
Later, some others than nobles adopted a seal, rich merchants, bourgeois, etc… and also cities.