A persistent claim holds that the hexagram is a Kabbalistic symbol of great antiquity, encoding the union of upward and downward forces, fire and water, the divine and the human. The interpretation is real and is genuinely held; the antiquity is not established.
What the older sources do contain is the hexagram as a protective device. It appears in magical and amuletic use across the medieval Mediterranean world, frequently under the name Seal of Solomon, and it is used in that role by Jews, Christians and Muslims alike, often interchangeably with the pentagram. The two names and the two shapes were not kept apart with any consistency, and the Arabic tradition of the seal is at least as rich as the Jewish one. Amulets are not emblems. A sign used to ward off harm is not thereby a sign of identity.
The name Magen David, shield of David, is attested in Jewish sources before the shape was firmly attached to it, and originally referred to divine protection rather than to a diagram. The joining of the name to the figure is medieval and gradual.
The symbolic readings offered today, the interpenetration of opposites, the six directions of space, the sefirot, were mostly supplied after the symbol had already become the accepted emblem, which is the usual order of events. It is worth saying plainly that this does not make them worthless. A community is entitled to invest a sign with meaning. But the historical claim and the devotional claim are different claims, and popular accounts routinely present the second as though it were the first.