METIS, Zeus' first wife, was one of the Oceanides or sea-nymphs. She was the personification of prudence and wisdom, a convincing proof of which she displayed in her successful administration of the potion which caused Cronus to yield up his children. She was endowed with the gift of prophecy, and foretold to Zeus that one of their children would gain ascendency over him.
In order, therefore, to avert the possibility of the prediction being fulfilled he swallowed her before any children were born to them. Feeling afterwards violent pains in his head, he sent for Hephæstus, and ordered him to open it with an axe. His command was obeyed, and out sprang, with a loud and martial shout, a beautiful being, clad in armour from head to foot. This was Athene (Minerva), goddess of Armed Resistance and Wisdom.
From: Berens, E.M. The Myths and Legends of Ancient Greece and Rome. New York: Maynard, Merril, & Co., 1880. Text in the public domain.