In the ancient Greek story of Pandora, the container she opened was originally called a pithos.
A pithos was a large storage jar used in the ancient Mediterranean for commodities such as grain, wine, or oil. Hesiod uses the Greek noun pithos when describing the vessel entrusted to Pandora. It was not necessarily a small box in the modern sense, but a substantial household container.
The phrase “Pandora’s box” became standard through later Latin and European retellings. The Renaissance scholar and translator Erasmus rendered the Greek vessel as a box, or pyxis, helping establish the familiar expression. English readers consequently often imagine a small decorated chest rather than a large jar.
The change in wording did not replace the basic mythic idea: Pandora opened a sealed container and released suffering into the human world, while one remaining good stayed inside.