Meaning

noun a decorative framework to conceal curtain fixtures at the top of a window casing

noun a molding at the corner between the ceiling and the top of a wall

noun the topmost projecting part of an entablature

originFrom Middle French corniche or Italian cornice, possibly from either (1) Latin cornīx (“crow”) or (2) Latin coronis (“curved line, flourish in writing”), from Ancient Greek κορωνίς (korōnís). See also corniche.

Etymology from Wiktionary, CC BY-SA 3.0