The Moon rules the subconscious mind, also known as "inner-self", where are our emotional desires, intuition, and habits.
The Moon symbol exists since 3500 years before BC. It has been found in Egypt, Greece, India, Byzantium and Sumer. The crescent moon symbolizes rebirth and immortality.
The Christians cherished it as the symbol of the Virgin Mary; in Asia, as the representation of cosmic forces; while for the Hinduisms, it represents our mind control.
The crescent moon was the symbol of Persian Empire and was set at the top of the Crowns. In 651, after the Arabs conquests, the crescent moon became the symbol of power in Occidental Asia. After the fall of Constantinople in 1453, it was definitely associated to Islam.