"A terrier is a dog of any one of many breeds or landraces of terrier type, which are typically small, wiry, very active and fearless dogs. Terrier breeds vary greatly in size from just a couple of pounds to weighing over 70 pounds and are usually categorized by size or function. There are five different groups with each group having several different breeds.
Most terrier breeds were developed in Great Britain and Ireland. They were used to control rats, rabbits, and foxes both over and under the ground. Some larger terriers were also used to hunt badgers. In fact, the word terrier comes from the Middle French terrier, derived from the Latin terra, meaning earth. The Kerry Blue Terrier and Airedale, however, are particularly noted for tackling river rats and otters in deep water. Different localities raised terriers suited to their hunting or vermin control needs. Terriers were crossed with hunting dogs, fighting dogs, and other terriers. In the mid 1800s, with the advent of dog shows, various breeds were refined from the older purpose-bred dogs. All of today's terrier breeds are bred primarily as pets."