The term mutt refers to a mixed-breed dog. It derives from the word muttonhead, suggesting stupidity. The term may be used in a derogatory fashion, or in an affectionate way. A mixed-breed dog might also be called a mongrel, and it is typically the result of random breeding rather than being specifically created from purebred dogs. A mutt is usually the result of generations of mixed-breed dogs or the unplanned breeding between purebreds. Some people believe that breed is very important, and there find it important to identify the ancestors of a dog that's mixed-breed.