The popular English expression gives Pandora’s container the name “box.” The phrase “Pandora’s box” refers to a source of unexpected troubles released by an action that cannot easily be undone.
The wording is a later translation tradition rather than Hesiod’s original terminology. In Works and Days, Hesiod describes a large storage vessel, commonly associated with the Greek word pithos. A pithos was a substantial earthenware container used in the ancient Mediterranean for storing goods such as grain, oil, or wine.
The “box” version became established through later retellings and translations, especially after the Renaissance. Erasmus is often credited with helping popularize the Latin phrase “pyxis Pandorae,” or “Pandora’s box,” in the sixteenth century.
This is why modern readers may encounter both “Pandora’s box” and “Pandora’s jar.” The mythological object is better represented by “jar” or “storage vessel” in the ancient context, but “box” is the canonical term in English idiom.