The English expression “It’s a dog’s life” and its variations illustrate just how pet ownership has changed in the Western world over the last 400 years. The most common meaning is of a life of poverty and want. Like other negative expressions involving the word dog, the phrase "a dog’s life" originated in the 16th century, when dogs and other house pets did not lead enviable lives. In the 20th century, however, Americans and other people around the world began offering preferential treatment to the animals that shared their homes. Consequently, the expression now sometimes means a pampered and easy life.
Dogs were domesticated by humans at least 15,000 years ago. The first pet dogs probably aided their human masters by protecting their homes, aiding hunting expeditions, and disposing of food scraps, roles still enjoyed by dogs today. This is not to say that dogs always enjoyed privileged roles in human households, however. For most of human history, they were treated like any other livestock. Some cultures even ate dogs when other food was scarce; some cultures still do.
In 16th-century England, dogs were kept by some wealthy landowners because of their well-known ability to trap or fetch prey during a hunt. When not working, these dogs were often housed outside, in rude kennels or whatever cover they could find. They were fed with table scraps, often vying with other dogs for these leftovers. Fleas and other parasites had free run of the dogs, of course, as even human hygiene was far below modern standards. These conditions led English people of the time to describe anyone suffering from poverty and a poor living standard as living “a dog’s life.”
Aside from “a dog’s life,” many other common dog-related expressions had their origin in this era. “To go to the dogs” means to go from prosperity to poverty, while “die like a dog” means to die in a miserable state. “Throw it to the dogs” recalls how the animals subsisted on unwanted scraps, while “in the doghouse” means to be excluded or ostracized. Various other phrases, such as “dirty dog,” are intended to insult or demean people by comparing them to these unfortunate 16th-century canines.
The 20th century was the dawn of a new era for the dog. Many families welcomed dogs into their homes and offered them increasingly ideal lifestyles. Lives of high-profile excess often included dogs; in 2007, New York real estate tycoon Leona Helmsley infamously left a fortune to her pet Maltese. This has led to a new definition of “a dog’s life,” meaning to have a carefree, pampered lifestyle. This reversal of fortune recalls yet another common expression, that “every dog has its day.”