A doggy bag is a container for taking leftovers home. Ask for a doggy bag.
The dog was always a polite fiction, since the food is for the person asking. Asking for a doggy bag is ordinary in America and still faintly awkward in Britain.
1noundoggy bagA container for taking leftovers home.
“The doggy bag fed him again the following evening.”
doggy bag is a container.
Doggy plus bag, from the polite pretence that the leftovers were for the dog.
From doggy + bag. In the food sense, this refers to the idea that the food is to be taken home for the diner's dog.
Etymology from Wiktionary, CC BY-SA
Practised in Restaurant & Cafe