Cur refers to a dog, usually of mixed ancestry. Fighting dogs that regress to growling rather than maintain calm are referred to as 'cur'. The derivation of the word "cur" is uncertain. According to the Dictionary of True Etymologies, "cur" is a Germanic word, possibly from Old Norse meaning to growl. If so, then the word is onomatopoeic, and a cur is a dog that goes "Grrr."
Cur is also a type of hunting dog developed in the United States. Cur is used to describe this type of dog, although it does not describe a specific breed. Breeds of cur are usually not recognized by major show registries, so selection for certain looks has not been a factor in their development. They were selected mainly for hunting ability, although some breeds of cur are also known for herding ability. As a result, in most of the cur breeds the appearance standard is extremely flexible, enough so that a complete breed appearance standard is difficult to create. The resultant diversity in appearance and selection for physical ability result in breeds that tend to be genetically sound and healthy.
Several kennel clubs register various cur breeds based on their ancestry (bloodlines), and several lines are recognized within each breed. The National Kennel Club has registered these breeds for decades and is famous for their organized hunting competitions.
Today the United Kennel Club has an active registration program and competition hunting program for these dogs.
Old Yeller was a cur and his intelligence and utility are typical.
Cur is also used in the play Rent to refer to a barking dog that "won't shut up". However, the phrase is used (technically) incorrectly as the dog in question is a purebred Akita.
Johannes Caius recorded in 1576 of the bloudthyrsty wolf that none of those noysome, and pestilent Beastes were left in the coastes of England and Wales.
The word cur appears to be colloquial in nature. In 1790, Thomas Bewick wrote:
The Cur Dog is a trusty and useful servant to the farmer and grazier; and, although it is not taken notice of by naturalists as a distinct race, yet it is now so generally used, especially in the North of England, and such great attention is paid in breeding it, that we cannot help considering it as a permanent kind. They are chiefly employed in driving cattle; in which way they are extremely useful. They are larger, stronger, and fiercer than the Shepherd's Dog; and their hair is smoother and shorter. They are mostly black and white colour. Their ears are half-pricked; and many of them are whelped with short tails, which seem as if they had been cut: These are called Self-tailed Dogs. They bite very keenly; and as they always make their attack at the heels, the cattle have no defence against them: In this way they are more than a match for a Bull, which they quickly compel to run. Their sagacity is uncommonly great. They know their master's fields, and are singularly attentive to the cattle that are in them: A good Dog watches, goes his rounds; and, if any strange cattle should happen to appear amongst the herd, although unbidden, he quickly flies at them, and with keen bites obliges them to depart.
Cur also appeared in the Scottish periodical, Blackwood's Magazine in 1819. The article, Species and Historic lineage of Canine derivations,penned by Sir P. Sean Lacey of London (1776 - 1842) cites "separating the miscreants and cur breeds from those of honorable standing".