The Whippet is a British breed of medium-sized dog of sighthound type. It is closely related to the Greyhound and – apart from its smaller size – closely resembles it. It has sometimes been described as "the poor man's greyhound". It is kept as a companion dog, and also for showing and for amateur racing and lure coursing. It has the highest running speed of any breed of its weight, and may have the fastest acceleration of any dog.The name is derived from an early seventeenth-century word, now obsolete, meaning "to move briskly".There has been continuity in describing Greyhound-types of different sizes: large, medium and small, recorded in hunting manuals and works on natural history from the Middle Ages. Edward of Norwich, 2nd Duke of York confirmed in his early fifteenth-century translation and additions to the original late fourteenth-century French Livre de chasse the advantage of maintaining the great, the middle, and the small size of greyhound for different sorts of game. The English physician and academic John Caius refers in his 16th century De Canibus Britannicus to lesser as well as greater sorts of Leporarius, Grehounde (greyhound) and notably to a type which has been connected to the Whippet, the Tumbler, a lesser sort of mungrell Greyhounde and excellent warren dog for catching rabbits, also recorded by the early 19th-century Scottish curator and editor Thomas Brown. The Victorian English writers describe the emerging modern breed of Whippet or snap-dog bred for catching rabbits, coursing competitions, straight rag-racing, and for the novel show fancy.