Why is it called a "hot dog" if it's not made out of dog?

The journey of the hot dog from a simple sausage to a staple of the American diet began in 1852 Germany, when the Frankfurt butchers' guild created a long, thin sausage and named it "frankfurter" in honor of their town. Shortly after that, someone noticed that the new sausage looked like a dachshund and started calling it a "dachshund sausage," after the long, thin dog. The name stuck and soon people were calling the frankfurter a dachshund sausage.

In 1906, Harry Mosley Stevens, who operated the New York Giant's ice cream and soda concession, decided to add the dachshund sausage to his menu. Stevens realized that in New York's cold spring afternoons the last thing anyone wanted was cold ice cream and that the dachshund sausage, which would stay warm in its skin and warmer still in a roll, was just the thing for his customers.

Stevens had his vendors hawk the sausage, instructing them to sell it by yelling, "They're red hot. Get your dachshund sausages while they're red hot."

While attending a game, Ted Dorgan, a leading cartoonist, saw the popularity of Stevens's new food idea and decided to lampoon it in a cartoon. In the cartoon, vendors were selling real dachshund dogs in a roll, yelling "Get your hot dogs!" at each other. As a result, the name "hot dog" caught on, and--after Stevens was able to convince people that it wasn't made out of dog meat--the hot dog became a hit.