In the novel Cujo, the St. Bernard is named Cujo.
Cujo begins as a friendly dog owned by the Camber family in Castle Rock, Maine. After being bitten by a rabid bat, he contracts rabies and becomes increasingly aggressive. The infection drives the central horror of the novel, as Donna Trenton and her young son Tad become trapped in a car at the Camber auto shop while Cujo guards the property.
The name is not a generic label for the breed or a nickname invented by the film. Stephen King used Cujo as the dog’s established name, and the book’s title comes directly from it. The story’s terror comes partly from the contrast between the large, normally dependable Saint Bernard and the diseased animal he becomes.
Readers sometimes mix Cujo up with Church, the resurrected cat from Pet Sematary, or with other King animals. Cujo is also the title of King’s 1981 novel and its 1983 film adaptation.