According to an ancient myth, Kea had abundant water (“ydor” in ancient Greek) and that is why it was once called “Hydroussa”. The Nymphs used to live on the island but they were forced to leave when a lion, which symbolizes drought, appeared. So, they moved from cape Leon to the neighboring town of Karystos. According to tradition, the Arcadians, who were led by Aristaeus, settled on the island. Aristaeus built an altar to Zeus Uvidus and he offered sacrifices to Sirius and Cronius Zeus. He seems to have been deified later, as well, and he was worshiped as Apollo Aristaeus on the island.
Another variation of the myth claims that he came from Thessaly. However, his worship is related to the ancient myth regarding the etesians which blew over the island during the summer heat period cooling people, animals and plants.
The island owes its name to a hero called Keos, who was the leader of the Locrians and conquered Kea in the 12th century BC. It was inhabited by the Minoans during the period of their thalassocracy and the Ionians, who were led by Thersidamantas.