In Greek mythology, Pandora’s contents were held in a pithos, a large storage jar.
The Greek word pithos described a substantial container used for storing goods such as grain, wine, or oil. Hesiod’s original account uses this term rather than the modern word “box.” The familiar English expression developed later through translation and interpretation.
Pandora opened the vessel after receiving it as part of the story of humanity’s origins. Once opened, it released the troubles that affect human life, while one thing remained inside. The jar’s size and storage function fit the agricultural world reflected in Hesiod’s poetry.
A common mix-up is assuming that the original Greek story specifically featured a small box. “Pandora’s box” is the standard modern phrase, but “Pandora’s jar” is closer to the wording of Hesiod’s surviving Greek text.