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Pentagrams were used symbolically in ancient Greece and Babylonia. The Pentagram has magical associations, and many people who practice pagan faiths wear them. Christians once commonly used the pentagram to represent the five wounds of Jesus[1][2], and it also has associations within Freemasonry.
The pentagram has long been associated with the planet Venus, and the worship of the goddess Venus, or her equivalent. It is also associated with the Roman Lucifer, who was Venus as the Morning Star, the bringer of light and knowledge. It is most likely to have originated from the observations of prehistoric astronomers.