In Hesiod’s account, the container Pandora opened is called a pithos, a large storage jar. The familiar phrase “Pandora’s box” arose later through a translation tradition rather than from the earliest Greek wording.
Hesiod’s Works and Days describes Pandora opening a sealed vessel that contained evils. A pithos was a substantial ceramic jar used in the ancient Greek world for storing commodities such as grain, oil, or wine. Its size and practical use differ from the small hinged box imagined in many modern illustrations.
The Latin humanist Erasmus helped popularize the box wording when he translated the Greek term into Latin as pyxis, meaning a box or small container. English and other languages then preserved the “box” expression.
Thus, “Pandora’s box” is the standard modern idiom, but “pithos” is the specific term associated with Hesiod’s original account.