Pandora’s box is an artifact in Greek mythology connected with the myth of Pandora in Hesiod’s Works and Days. The container mentioned in the original story was actually a large storage jar but the word was later mistranslated as “box.”
According to Hesiod, when Prometheus stole fire from heaven, Zeus, the king of the gods, took vengeance by presenting Pandora to Prometheus’ brother Epimetheus. Pandora opened a jar left in his care containing sickness, death and many other unspecified evils which were then released into the world. Though she hastened to close the container, only one thing was left behind – usually translated as Hope, though it could also have the pessimistic meaning of “deceptive expectation”.

From this story has grown the idiom “to open (a) Pandora’s box”, meaning to do or start something that will cause many unforeseen problems. Its modern, more colloquial equivalent is “to open a can of worms”.

There were alternative accounts of jars or urns containing blessings and evils bestowed upon humanity in Greek myth, of which a very early account is related in Homer’s Iliad:

On the floor of Jove’s palace there stand two urns, the one filled with evil gifts, and the other with good ones. He for whom Jove the lord of thunder mixes the gifts he sends, will meet now with good and now with evil fortune; but he to whom Jove sends none but evil gifts will be pointed at by the finger of scorn, the hand of famine will pursue him to the ends of the world, and he will go up and down the face of the earth, respected neither by gods nor men.

In a major departure from Hesiod, the 6th-century BC Greek elegiac poet Theognis of Megara states that

Hope is the only good god remaining among mankind;
the others have left and gone to Olympus.
Trust, a mighty god has gone, Restraint has gone from men,
and the Graces, my friend, have abandoned the earth.
Men’s judicial oaths are no longer to be trusted, nor does anyone
revere the immortal gods; the race of pious men has perished and
men no longer recognize the rules of conduct or acts of piety.

Giulio Bonasone’s 16th century engraving of Epimetheus opening the fatal jar
The poem seems to hint at a myth in which the jar contained blessings rather than evils. It is confirmed in the new era by an Aesopic fable recorded by Babrius, in which the gods send the jar containing blessings to humans. Rather than a named female, it was a generic “foolish man” (ἀκρατὴς ἄνθρωπος) who opened the jar out of curiosity and let them escape. Once the lid was replaced, only hope remained, “promising that she will bestow on each of us the good things that have gone away.” This aetiological version is numbered 312 in the Perry Index.

In the Renaissance, the story of the jar was revisited by two immensely influential writers, Andrea Alciato in his Emblemata (1534) and the Neo-Latin poet Gabriele Faerno in his collection of a hundred fables (Fabulum Centum, 1563). Alciato only alluded to the story while depicting the goddess Hope seated on a jar in which, she declares, “I alone stayed behind at home when evils fluttered all around, as the revered muse of the old poet [Hesiod] has told you”.[17] Faerno’s short poem also addressed the origin of hope but in this case it is the remainder of the “universal blessings” (bona universa) that have escaped: “Of all good things that mortals lack,/Hope in the soul alone stays back.”

An idea of the nature of the blessings lost is given in a Renaissance engraving by Giulio Bonasone, where the culprit is Pandora’s husband, Epimetheus. He is shown holding the lid of a large storage jar from which female representations of the Roman virtues are flying up into the air. They are identified by their names in Latin: security (salus), harmony (concordia), fairness (aequitas), mercy (clementia), freedom (libertas), happiness (felicitas), peace (pax), worth (virtus) and joy (laetitia). Hope (spes) is delayed on the lip and holds aloft the flower that is her attribute.