The word “sour” is deployed in literature with a rich duality, serving both literal and metaphorical purposes. In some texts it describes an actual taste or state, as when ingredients turn unpleasantly tangy or food deteriorates ([1], [2]), whereas in others it evokes a mood or character trait—suggesting bitterness, misfortune, or a gloomy temperament ([3], [4], [5], [6]). At times, it encapsulates emotional reactions or allegorical commentary, as when characters’ discontent is painted with “sour” expressions or adversities are labeled as “sour misfortune” ([7], [8], [9]). Even references to “sour grapes” or “sour faces” extend its reach into proverbial territory, underlining themes of envy, decay, and disappointment ([10], [11], [12]). In each context, its flexibility adds vividness, whether highlighting the physical transformation of a substance or the inner workings of a character’s disposition.