The English word dog can be traced back to the Old English docga, a "powerful breed of canine". The term may derive from Proto-Germanic *dukkÅn, represented in Old English finger-docce ("finger-muscle"). Due to the linguistically archaic structure of the word, the term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal.
The English word dog, in common usage, refers to the domestic pet dog, Canis lupus familiaris. The species was originally classified as Canis familiaris and "Canis familiarus domesticus" by Linnaeus in 1758. In 1993, dogs were reclassified as a subspecies of the gray wolf, Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists.
