Before it was common practice for people to feed dog food to their canines, they would often give them table scraps instead. This practice was continued whenever individuals would eat at a restaurant, and many people brought a paper sack with them to carry leftovers home in. As such, this sack became known as a "doggy bag". The term is still used today, and many restaurants provide foam or plastic containers for their patrons rather than paper bags.
At one time, people fed their pets leftovers from the dinner table rather than buying them dog food. Whenever pet owners ate out, they would consider this fact and often bring along a paper bag to put the table scraps in, usually a few leftover pieces of meat or potatoes or even bones in some instances. A restaurant owner would often place additional scraps from the kitchen in the paper bag, especially if it were very near closing time.
As it is now more common to feed dog food to canines, the purpose of a doggy bag has shifted. People still take leftovers home, but they do so in order to eat some of the food at another time. This is often because the portions are served are too large to be eaten in one setting, and diners do not wish to waste their money on food they are unable to consume.
It is uncertain where the term "doggy bag" originated, although many believe it to be an Old English saying. This may be due in part to the fact that this idiom is more common in England and the United States than in other parts of the world. Although the phrase is recognized throughout England, many people there no longer adhere to this practice because the portion sizes in restaurants there are much smaller than in the U.S.
Even though people still take leftovers home, they do not usually bring their own doggy bag. This is because many restaurants are accustomed to the practice and provide special containers for their customers to store food in. These are typically foam boxes with a hinged lid or a plastic container with a snap-on lid. A paper bag may still be used whenever people are dining in a fast-food restaurant. These containers are typically provided at no charge to guests, so people do not need to feel embarrassed when asking for one of these "to-go boxes".