Dog

The domestic dog is a domesticated canid which has been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes.

Although initially thought to have originated as a manmade variant of an extant canid species  extensive genetic studies undertaken during the 2010s indicate that dogs diverged from an extinct wolf-like canid in Eurasia 40,000 years ago.

 

 Being the oldest domesticated animal, their long association with people has allowed dogs to be uniquely attuned to human behavior, as well as thrive on a starch-rich diet which would be inadequate for other canid species. Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding handicapped individuals. This impact on human society has given them the nickname "man's best friend" in the Western world. In China and South Vietnam dogs are a source of meat for humans.

Etymology

The term "domestic dog" is generally used for both domesticated and feral varieties. The English word dog comes from Middle English dogge, from Old English docga, a "powerful dog breed". The term may possibly derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle"). The word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others. The term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary.

In 14th-century England, hound (from Old English: hund) was the general word for all domestic canines, and dog referred to a subtype of hound, a group including the mastiff. It is believed this "dog" type was so common, it eventually became the prototype of the category "hound". 
By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. The word "hound" is ultimately derived from the Proto-Indo-European word *kwon- "dog".

In breeding circles, a male canine is referred to as a dog, while a female is called a bitch (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja). A group of offspring is a litter. The father of a litter is called the sire, and the mother is called the dam. Offspring are, in general, called pups or puppies, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp