The ankh represents the union of man and woman and symbolizes the creation of life through this union. According to one of the theories about it's origins, the symbol could be the combination of the male and female archetypes, representing Osiris and Isis, the cross and the oval, respectively.
It was believed that the union of Osiris and Isis flooded the Nile every year and gave life to Egypt by providing fertility. That is why the symbol is also known as “the Key of the Nile” and why it is considered to represent the union of heaven and earth.
The origin of the Ankh Symbol is not entirely well known, but it can be seen in the Egyptian hieroglyphic writing. The Ankh was taken by the Hebrews from the Egyptians and was introduced to the language by Moses, who was instructed in the wisdom of the priests of Egypt along with many other mystical words.