Cognoscente: Someone possessing superior knowledge in a particular field, usually the arts; a connoisseur, an aficionado, a discerning expert. 

I get the feeling a “cognoscente” is likely a member of the Illuminati of the art world.  Or, based on modern art purchases, perhaps the “cognoscente” is simply a gullible person with a large checking account.

Cognoscente derives from its now obsolete Italian twin: cognoscente (now conoscente).  Naturally, the Italian word comes from the Latin verb cognosco (I know). 

The Latin cognosco comes from the Latin preposition con (with) and the Greek word γιγνώσκω (gignosko) meaning, “I know.”