The story
From the Aesop's fable The Goose that Laid the Golden Eggs, in which a married couple own a goose that lays one golden egg every day. Because of greed, they decide to kill the goose to obtain all the gold they suppose to be present in its body. Once opened, the goose proves to be like any normal goose inside.
Etymology from Wiktionary, CC BY-SA 4.0.