a small bag provided on request by a restaurant for a customer to carry home leftovers of a meal, ostensibly to feed a dog or other pet.
Origin of doggy bag
An Americanism dating back to 1965–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a bag into which leftovers from a meal may be put and taken away, supposedly for the diner's dog
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012