Pepsi

Originally short for Pepsi-Cola, coined in 1898 as a renaming of the brand from "Brad's Drink", in order to imply that the fizzy drink could cure dyspepsia. While some have suggested Pepsi is short for the digestive enzyme pepsin, sometimes with the assumption that pepsin was used as an ingredient in Pepsi, this is a folk etymology, as there is no official confirmation of it nor any evidence for a link between the enzyme and the beverage. Nonetheless, both the words pepsin and dyspepsia ultimately derive from Ancient Greek πέψις (pépsis), which means “cooking, fermentation or digestion”. (Compare Italian pepsi, from the same source.) (person from Quebec): In reference to their supposed love of junk food.

来源：wiktionary