The story
Unknown, first attested in The John-Donkey (July 29, 1848, page 47), popularized by the National Biscuit Company with the slogan Polly wants a cracker?
Etymology from Wiktionary, CC BY-SA 4.0.
Polly want a cracker
Today it means: A line stereotypically repeated by parrots that have been trained to talk. Full definition →