Smart aleck

Someone irritatingly smug about being clever or knowledgeable. Current informal and mildly insulting Regional use: United States, with early Western concentration.

American slang first securely printed in an 1863 California newspaper and common in Western examples soon after. The identity of the supposed original Aleck or Alec is unknown. Confidence man Aleck Hoag has been proposed, but no evidence links his name to the phrase; early geography actually points more strongly to the American West than to Hoag's New York underworld.