Smart Alec/Aleck

This expression which describes an obnoxious know-all, is originally American in origin, and dates from the mid-19th century. The expression was adopted on the other side of the Atlantic by the early 20th century. The source often given is Aleck Hoag, an American confidence trickster operating in New York during the 1840s, but this is not proven beyond doubt. Smart arse and the American smart ass are more modern, less polite equivalents.