1Attributive and in the genitive. Designating a type of spaniel; (in later use) specifically a small breed of spaniel, having a high, rounded head, short nose, large eyes and long, hanging ears; a dog of this breed, as "King Charles spaniel", "King Charles's spaniel", etc.
2A King Charles spaniel.
Late 18th century; earliest use found in William Smellie (1740–1795), printer, editor, and author. From King Charles, the name of two kings of England, Scotland, and Ireland: Charles I, who was beheaded during the English Civil War, and his son, Charles II.