The term 'grapes of wrath' is a biblical allusion. There is no one element in the story that corresponds to the grapes. It is referring to a passage that talks figuratively aout God judging the...
This is a reference to The Apocalyspse of Saint-John (And the angel thrust in his sickle into the earth, and gathered the vine of the earth, and cast it into the great winepress of the wrath of God)...