know as much about as a hog knows about Sunday
know as much about (something) as a hog knows about Sunday
To know absolutely nothing about something. Primarily heard in US. My uncle bequeathed the farm to me when he passed away, but I knew as much about running a farm as a hog knows about Sunday! Oh, stop lecturing me. You know as much about running a business as a hog knows about Sunday!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
know as much about something as a hog knows about Sunday
Rur. to have no knowledge of something. Don't let Jim make dessert for the picnic. He knows as much about pies as a hog knows about Sunday. I had quite a time changing the tire, since I know as much about cars as a hog knows about Sunday.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.