The symbol of the hexagram, the star-like figure formed by two triangles, has many connotations, especially when it is enclosed by a circle; super-natural powers have been attributed to it in many parts of the world since ancient times.
In Europe, the pentagram is usually known as King Solomon's Seal, while the hexagram is known as the Star of David; and it is often assumed that this was always the case....
However, the evidence points to the gradual evolution of the hexagram from a Roman cosmological symbol to a religious and magical symbol which was not specifically connected to one religion or people. Research suggests that both motifs were used by different religions and that the clearest meaning of the hexagram is associated with magical techniques to ward off evil forces.
http://www.mfa.gov.il/MFA/MFAArchive/1990_1999/1999/2/King%20Solomon-s%20Seal