In Hesiod's version of Pandora's box, the container was originally called a pithos.
A pithos was a large Greek storage jar, generally made from clay and used for commodities such as grain, oil, or wine. Hesiod used this ordinary household object in a myth explaining why suffering and hardship exist in human life. The vessel was not described as a small hinged box.
The two main surviving accounts of Pandora come from Hesiod's Theogony and Works and Days, composed in archaic Greece. In Works and Days, the jar holds evils that escape when Pandora opens it. The text does not use the modern English expression “Pandora's box.”
The box image became standard through a translation history. Erasmus of Rotterdam translated the Greek term into Latin as pyxis, meaning a box or small container, rather than preserving the more accurate pithos. Later European retellings popularized the familiar phrase, which remains better known than the original object.