common as an old shoe
(as) common as an old shoe
Lacking in manners or refinement. I can't believe he just put his elbows on the dinner table—why, he must be as common as an old shoe! Everyone thinks I'm common as an old shoe just because of the way I talk. Why on earth did you invite men who are common as an old shoe to such a fancy event?
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
*common as an old shoeand *common as dirt
low class; uncouth. (*Also: as ~.) That ill-mannered girl is just as common as an old shoe. Despite Mamie's efforts to appear to be upper class, most folks considered her common as dirt.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.