Lemon

British and American informal for something that is worthless or not the genuine article as in, for example, ‘the car I bought was a lemon’ dates from the late 19th/early 20th century and supposedly derives from the metaphor of leaving a sour taste in the mouth, which of course lemons do. This usage far pre-dates the appearance of lemon symbols in fruit machines, which is sometimes misguidedly given as the origin.