A Cairn terrier mixed with a Chihuahua is known as a Toxirn by the American Canine Hybrid Club. The Designer Dogs Kennel Club, the International Designer Canine Registry and the Designer Breed Registry refer to this hybrid breed as a Cairn-chi or Cairnchi.
Cairn terriers were bred in Scotland as small-game hunting dogs, able to flush out prey from rock piles, known as cairns. Chihuahuas are a toy breed of dog originating from the eponymous Mexican state. Since both of these breeds are small, the Toxirn mix usually weighs only 6 to 18 pounds. Its coat tends to be a mixture of the shaggier terrier fur and the shorter hair of the Chihuahua.