c.1200, cointe, "cunning, ingenious; proud," from Old French cointe "knowledgeable, well-informed; clever; arrogant, proud; elegant, gracious," from Latin cognitus "known, approved," past participle of cognoscere "get or come to know well" (see cognizance). Modern spelling is from early 14c.
Later in English, "elaborate, skillfully made" (c.1300); "strange and clever" (mid-14c.). Sense of "old-fashioned but charming" is first attested 1795, and could describe the word itself, which had become rare after c.1700 (though it soon recovered popularity in this secondary sense). Related: Quaintly; quaintness.