The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with put up or shut up
Act on what you are saying or stop talking about it, as in You've been citing evidence for months but never presented it—now put up or shut up. This somewhat impolite term, often put as a command, is believed to come from gambling, in which a card player is told to ante up or withdraw. A second theory maintains that it means either put up your fists to fight or back down.