Cognoscenti, know, can, cognition, and diagnosis all share the same PIE root — the word "to know" is one of the largest families in all Indo-European languages.
People who are well-informed and knowledgeable about a particular subject, especially in the arts. Connoisseurs or experts.
From Italian cognoscenti, plural of cognoscente (one who knows, a connoisseur), from Latin cognoscens, present participle of cognoscere (to learn, know, recognize), from co- (together) + gnoscere/noscere (to know) Key roots: cognoscere (Latin: "to learn, know, recognize"), *ǵneh₃- (Proto-Indo-European: "to know").
Cognoscenti shares its PIE root *ǵneh₃- (to know) with an enormous family: cognition, recognize, cognate, connoisseur, know, knowledge, gnosis, diagnosis, prognosis, ignorant, incognito, and even "can" (from Germanic *kunnaną, 'to know how'). The Italian plural form cognoscenti is used in English as both singular and plural — a grammatical import that preserves the Italian plural 'i' ending. The word carries a subtle connotation of elitism that "expert" or "specialist"