Ever since the Middle Ages, to lead "a dog's life" meant to live miserably. If you had "gone to the dogs," you were ruined. "Dog towns" were unimportant, "dog cheap" was cheap, indeed,. An unsuccessful book, a bad show at the theater, and a losing horse were - and still are - dogs.
Or is it a hound?
Although the dog was probably the first domesticated animal, the word "dog" was not its original, Old English name. This animal was generally called "hund," which evolved into the modern word "hound." In time, "docga" usurped "hund" and the name spread to other languages as a name for a specific breed. It influenced French "dogue" (mastiff); Spanish "dogo" (terrier); Swedish "dogg" (bulldog); and German "dogge" (Great Dane). By the 13th century, a "hound" was strictly a hunting dog.
Dog-eat-dog; the real story
This expression for cutthroat competition originated in a misinterpretation of a much earlier saying that dogs do not eat their own kind. The old wisdom went like this: "Dogs are hard drove, when dogs eat dogs." And then, "It is a hard winter, when dogs eat dogs." The 18th-century phrases expressing desperate conditions lay dormant for centuries until pulled out of context to suggest ruthless self-interest.
Hot dog: easier to spell
This shorthand term for a frankfurter really did refer to a dog. At the turn of the century, sports cartoonist T.A. Dorgan innocently began a rumor that the popular "franks" contained dog meat by creating a caricature of a dachshund on a bun. Supposedly, Harry Stevens, who owned a ballpark food concession, first sold the sausages in buns. Because of their resemblance to the short-legged, long-bodied dachshund, he called them "dachshund sausages."
Dorgan avoided the breed's tricky spelling and simply called it a "hot dog." The Coney Island, N.Y., chamber of commerce was so alarmed by the implications of the term that in 1913 they banned the term from the boardwalk.
Dogs - and ponies
The term "dog and pony show" is fairly recent: 1957 is the first cite that etymologists have found. It refers to "an elaborate formal occasion or undertaking usually for public relations purposes," according to one dictionary. It's often used in reference to a business presentation or sales pitch before a group. The image is that of a circus act in which trained dogs leap on and off the backs of trained ponies - in exactly the same sequence each time.