A stubborn and durable person: He's a tough cookie. He isn't going to talk, threats or no threats(1928+)
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
Examples from the Web for tough cookie
Contemporary Examples
Added Poitier, “She was a tough cookie with a heart of gold.”