The development of the modern heraldic language cannot be attributed to a single individual, time, or place. Although certain designs that are now considered heraldic were evidently in use during the eleventh century, most accounts and depictions of shields up to the beginning of the twelfth century contain little or no evidence of their heraldic character. For example, the Bayeux Tapestry, illustrating the Norman invasion of England in 1066, and probably commissioned about 1077, when the cathedral of Bayeux was rebuilt, depicts a number of shields of various shapes and designs, many of which are plain, while others are decorated with dragons, crosses, or other typically heraldic figures. Yet no individual is depicted twice bearing the same arms, nor are any of the descendants of the various persons depicted known to have borne devices resembling those in the tapestry.
Similarly, an account of the French knights at the court of the Byzantine emperor Alexius I at the beginning of the twelfth century describes their shields of polished metal, utterly devoid of heraldic design. A Spanish manuscript from 1109 describes both plain and decorated shields, none of which appears to have been heraldic. The Abbey of St. Denis contained a window commemorating the knights who embarked on the Second Crusade in 1147, and was probably made soon after the event; but Montfaucon's illustration of the window before it was destroyed shows no heraldic design on any of the shields.
In England, from the time of the Norman conquest, official documents had to be sealed. Beginning in the twelfth century, seals assumed a distinctly heraldic character; a number of seals dating from between 1135 and 1155 appear to show the adoption of heraldic devices in England, France, Germany, Spain, and Italy. A notable example of an early armorial seal is attached to a charter granted by Philip I, Count of Flanders, in 1164. Seals from the latter part of the eleventh and early twelfth centuries show no evidence of heraldic symbolism, but by the end of the twelfth century, seals are uniformly heraldic in nature.
One of the earliest known examples of armory as it subsequently came to be practiced can be seen on the tomb of Geoffrey Plantagenet, Count of Anjou, who died in 1151. An enamel, probably commissioned by Geoffrey's widow between 1155 and 1160, depicts him carrying a blue shield decorated with six golden lions rampant. He wears a blue helmet adorned with another lion, and his cloak is lined in vair. A medieval chronicle states that Geoffrey was given a shield of this description when he was knighted by his father-in-law, Henry I, in 1128; but this account probably dates to about 1175.
The earlier heraldic writers attributed the lions of England to William the Conqueror, but the earliest evidence of the association of lions with the English crown is a seal bearing two lions passant, used by the future King John during the lifetime of his father, Henry II, who died in 1189. Since Henry was the son of Geoffrey Plantagenet, it seems reasonable to suppose that the adoption of lions as an heraldic emblem by Henry or his sons might have been inspired by Geoffrey's shield. John's elder brother, Richard the Lionheart, who succeeded his father on the throne, is believed to have been the first to have borne the arms of three lions passant-guardant, still the arms of England, having earlier used two lions rampant combatant, which arms may also have belonged to his father. Richard is also credited with having originated the English crest of a lion statant (now statant-guardant).
The origins of heraldry are sometimes associated with the Crusades, a series of military campaigns undertaken by Christian armies from 1096 to 1487, with the goal of reconquering Jerusalem and other former Byzantine territories captured by Muslim forces during the seventh century. While there is no evidence that heraldic art originated in the course of the Crusades, there is no reason to doubt that the gathering of large armies, drawn from across Europe for a united cause, would have encouraged the adoption of armorial bearings as a means of identifying one's commanders in the field, or that it helped disseminate the principles of armory across Europe. At least two distinctive features of heraldry are generally accepted as products of the crusaders: the surcoat, an outer garment worn over the armor to protect the wearer from the heat of the sun, was often decorated with the same devices that appeared on a knight's shield. It is from this garment that the phrase "coat of arms" is derived. Also the lambrequin, or mantling, that depends from the helmet and frames the shield in modern heraldry, began as a practical covering for the helmet and the back of the neck during the Crusades, serving much the same function as the surcoat. Its slashed or scalloped edge, today rendered as billowing flourishes, is thought to have originated from hard wearing in the field, or as a means of deadening a sword blow and perhaps entangling the attacker's weapon.