Smart alec and smart aleck are two spellings of the same expression, one of which is used much more frequently. We will examine the definition of the terms smart alec and smart aleck, where they came from, which spelling is used more frequently and some examples of that use in sentences.
A smart alec or smart aleck is someone who believes he is knowledgeable about everything, or someone who behaves as if he is more clever than everyone else. A smart alec is extremely obnoxious to deal with. Though the origin of the terms smart alec and smart aleck is far from certain, professor Gerald Cohen believes the expression may be traced to a New York thief named Alex Hoag, active during the 1840s. This theory indicates that Hoag, in cooperation with his prostitute wife Melinda, stole from her clients. Hoag bribed policemen of the era in order to escape prosecution. In the end, Hoag became too smart for his own good and stopped paying the police to look the other way. He was arrested.
The spellings smart alec and smart aleck are both listed by the Oxford English Dictionary as being acceptable, but the spelling smart aleck is about four times more popular than the smart alec spelling. Note that in neither case is the word alec or aleck capitalized. When used as an adjective before a noun, the terms are hyphenated as in smart-alec and smart-aleck.
Examples
Her move follows a row on Wednesday between the pair in the Dáil chamber, where Leo Varadkar claimed that it was “no wonder” the Stormont assembly was in hiatus given Sinn Féin’s “attitude, smart alec remarks, lack of temperance, lack of respect for other people, inability to listen to them, and inability to listen to compromise”. (The Times)
But only Tig wants to address what happened, often through what Bill calls her “smart aleck” jokes, her reflexive method for jimmying locked family doors. (The New Yorker)