1714, "a critical judge of any art, one well-acquainted with any of the fine arts and thus competent to pass judgment on its products," from French connoisseur (Modern French connaiseur), from Old French conoisseor "an expert, a judge, one well-versed," from conoistre "to know," from Latin cognoscere "to get to know, recognize, become well-acquainted with," from assimilated form of com "with, together" (see con-) + gnoscere "recognize" (from PIE root *gno- "to know").
Transferred sense of "a critic in matters of taste (in food, wine, etc.) is from 1796. The attempt in 183. to introduce a corresponding abstract noun connoissance did not succeed. Related: Connoisseurship.