"Imp" before a name can mean a couple of things. If it is before the name, as you suggest, it could be part of the horse's name because there is a family line in the Standardbred industry that uses the word "Imp" in their names. The "Imp" designation can also mean "imported," but usually the country or letter of the country will follow the name of a racehorse without the "Imp"; for example, Pacific Flight N (from New Zealand) or Gidigan A (from Australia).
