The Terrier group

The name comes from the Latin terra, meaning earth, which tells you where terriers were meant to work. The short-legged breeds were bred to go underground after rats and other vermin. The long-legged ones dig their quarry out rather than tunneling in after it. The group also includes the "bully" breeds, which were created for grim blood sports like bull-baiting that have long since been outlawed, and today they're popular companions. Terriers are known for being feisty and determined, and they still shine in Earthdog, a sport built around the tunnel work they were bred for.

Sources: American Kennel Club, The 7 AKC Dog Breed Groups Explained