In the Pandora myth, the Greek name for the large storage jar later called a box is pithos. Hesiod’s Works and Days uses the word pithos for the container entrusted to Pandora, not a small wooden box.
A pithos was a large earthenware storage vessel used in the ancient Greek world for commodities such as grain, wine, or oil. Its size and practical function make it very different from the compact box shown in many modern illustrations. The familiar English phrase arose through a later translation tradition.
The Renaissance scholar Desiderius Erasmus translated the Greek vessel as a Latin term meaning a box or small container, helping establish the expression “Pandora’s box.” The myth itself says that the evils escape from the vessel, while hope remains inside. This translation history is why the popular phrase differs from the ancient wording.