In the Greek myth of Pandora’s box, the troubles were originally kept in a pithos, a large storage jar. The familiar “box” is the result of a later translation tradition, not the vessel described in the earliest surviving Greek account.
Hesiod uses the ancient Greek word pithos in Works and Days. A pithos was a substantial ceramic container used to store commodities such as grain, wine, or oil. These jars could be large enough to stand taller than a person, making the image very different from a small hinged box.
The Latin humanist Erasmus helped popularize the box wording through a translation choice involving the Greek term pyxis, meaning a small box. Modern retellings therefore usually say “Pandora’s box,” while scholars often point out that “Pandora’s jar” is closer to Hesiod’s text.