Con′nois‐seur″ (?; 277), n. [F. connaisseur, formerly connoisseur, fr. connaître to know, fr. L. cognoscere to become acquainted with; co- + noscere, gnoscere, to learn to know. See Know, and cf. Cognizor.] One well versed in any subject; a skillful or knowing person; a critical judge of any art, particulary of one of the fine arts.
The connoisseur is “one who knows,” as opposed to the dilettant, who only “thinks he knows.”
Fairholt.