Hesiod used the Greek word pithos for the container later popularly called Pandora’s box. A pithos was a large storage jar used in the ancient Greek world, often for grain, wine, oil, or other goods. Hesiod’s Works and Days therefore presents Pandora opening a jar, not a small hinged box.
The “box” wording became established much later through a Renaissance translation associated with the humanist Erasmus. His Latin rendering used pyxis, a word meaning box or small container, and that translation helped create the form now familiar in English and many other languages.
This is a common mix-up rather than a minor vocabulary detail. Artistic depictions frequently show Pandora opening a box because the later phrase is so widespread, while classical references to the original poem should identify the object as a pithos. The distinction also explains why ancient vase paintings and modern illustrations can portray the same episode with visibly different containers.