a green or bluish patina formed on copper, brass, or bronze surfaces exposed to the atmosphere for long periods of time, consisting principally of basic copper sulfate.
1300, from O.Fr. verte grez (13c.), verte de Grece (c.1170), lit. "green of Greece," from obs. Fr. verd, from L. viridis (see verdure). The reason for it being called that is not known.