In Greek mythology, Hesiod said Pandora opened a pithos, a large storage jar, rather than a box.
The word pithos is the Greek term used in the relevant ancient account. Pithoi were substantial ceramic containers used to store goods such as grain, oil, or wine. Their size and shape were very different from the small hinged boxes shown in many modern illustrations.
The expression “Pandora’s box” became standard through later translation and cultural transmission. Erasmus of Rotterdam is often credited with popularizing the box wording in the sixteenth century, helping the phrase move from a specific mythological object into a general English idiom.
This is a common mix-up, but it does not change the central plot: opening the container releases evils into the human world, while hope remains inside. The exact interpretation of the jar’s contents is debated, but its original form is a pithos.