A “smart alec” is an obnoxious or conceited know-it-all.
The Encyclopedia of Word and Phrase Origins by Robert Hendrickson says: “If there ever lived a real ‘smart Aleck,’ an Alexander so much of an obnoxiously conceited know-it-all that his name became proverbial, no record of him exists. The term can be traced back to about the 1860s and is still frequently used for a wise guy today. The original ‘smart aleck’ may have been at least clever enough to cover up all traces of his identity.”
From the Morris Dictionary of Word and Phrase Origins by William and Mary Morris: “Its first recorded appearance in print was in a Carson City, Nevada, newspaper in 1862. But history doesn’t record who the first ‘smart alec’ was. Many years later there was a prodigiously vain figure on the New York literary scene called Alec – Alexander Woollcott – but the expression ‘smart alec’ was well established long before his time.”
And, from The Times, on May 9, 2002: “The phrase ‘Smart Alec,’ meaning a conceited know-it-all, dates back to mid-1800s America. Regarding the identity of ‘Alec,’ most American dictionaries point to Alec Hoag, a notorious pimp and thief who operated in New York in the 1840s. He operated a trick called “The Panel Game” where he would sneak in via gaps in the walls and steal the valuables of his sleeping or unwary clients. The reputation he generated for not getting caught earned him the nickname Smart Alec.”
Research done by Professor Gerald Cohen in 1985 for Studies of Slang Part 1, as well as research by other historians, indicates—based on considerable newspaper article evidence—means that the ‘Alec Hoag’ theory for the source of the phrase may be true.
Apparently, to protect himself and his wife from arrest, Hoag enlisted a couple of police officers by promising to split the stolen goods with them. But Hoag’s downfall came when he ran into some financial difficulties and couldn’t give the officers their fair share.
The police soon arrested Hoag and his wife, Melinda. Alec Hoag was then given the nickname “Smart Alec” by the police for being too smart for his own good.
When I was in high school, “smart alec” was what we called someone who sassed the teachers or pulled off stupid pranks. I may have been a scallywag, but never aspired to the title of smart alec.