The word, "Easter" is derived from the old English word "Eostre," which in turn is derived from the Old High German word "Ostara." Ostara or Eostre was a pagan fertility goddess in Saxon and Germanic traditions. The tradition of Eostre is probably derived from the ancient Greek goddess Eos, who was the goddess of the dawn. Many variations of this name and tradition exist throughout Norse, Germanic and Indo-European cultures. It is also related to the terms "estrus" and "estrogen." In ancient Greek times, "estrus" meant "frenzy" or "mad impulse." In Greek mythology, "estrus" was the fly that Hera sent to torment Io.