Hesiod said Pandora opened a pithos, a large Greek storage jar.
The Greek word pithos referred to a substantial container used for storing goods such as grain, oil, or wine. In Works and Days, Hesiod describes Pandora lifting the lid of this vessel, releasing the troubles that had been contained inside.
The familiar English phrase “Pandora’s box” developed much later. The Renaissance scholar and translator Erasmus used the Latin expression pyxis, meaning box or small container, helping establish the wording that became standard in European languages.
A pithos was not a small decorative box. Ancient examples could be very large and were often kept partly buried for stability. The change from jar to box is therefore one of the best-known translation shifts in the history of the myth.