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Dumb as a door knob.

Posted by Emily C. on June 23, 2003

Has anyone heard or used the phrase 'Dumb as a door knob"? What are it's origins, I can't find anything?!

Also, along the same lines, what is the origin of using the term 'knob' to describe someone, such as "He walked right into the steel post, what a knob!"?