Pandora’s container is called a pithos in the original Greek tradition. A pithos was a large storage jar used in the ancient Greek world, and Hesiod uses that kind of vessel in the Pandora story.
The word matters because “Pandora’s box” is not the literal wording of the earliest account. Erasmus and later European tradition helped popularize a box through the Latin term pyxis, which can mean a small container or box. English then retained the box image, making it one of the world’s most recognizable mythological expressions.
A pithos was much larger and more practical than the small box shown in many illustrations. Such jars could store agricultural goods, including grain, oil, or wine. The vessel’s storage function also suits the myth’s image of troubles being held together before they enter human life. “Pandora’s jar” is therefore closer to Hesiod’s object than the conventional English phrase.