A small, cheap restaurant, lunchroom, or diner: The Marx brothers ate in coffee pots and greasy spoons/ your above-average greasy spoon in Boston's Back Bay(1925+)
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 greasy spoon
A cheap restaurant, especially one serving short-order fried foods. For example, College students short of cash tend to eat a lot in that greasy spoon. This expression also implies that the restaurant is not very clean.
[ c. 1900