Till the cows come home
What's the meaning of the phrase 'Till the cows come home'?
For a long but indefinite time.
What's the origin of the phrase 'Till the cows come home'?
Cows are notoriously languid creatures and make their way home at their own unhurried pace. That's certainly the imagery behind 'till the cows come home' or 'until the cows come home', but the precise time and place of the coining of this colloquial phrase isn't known.
It is a long-standing expression and the earliest example if it in print comes from the late 16th century. John Eliot used it in Ortho-epia Gallica, 1593, which was a French teaching textbook in which he attempted to "teacheth to speake truely, speedily and volubly the French-tongue":
I am tied by the foote till the Cow come home.
It's worth mentioning that this and other early citations refer to one cow coming home, why the phrase later migrated into the plural isn't clear.
Groucho Marx was never one to pass up an opportunity for a play on words, like this dialogue of the 1933 film Duck Soup:
"I could dance with you till the cows come home. Better still, I'll dance with the cows and you come home."
[My thanks to Peter Lukacs, ElizabethanDrama.org for the 1593 citation.]