Patina

[pat-n-uh, puh-tee-nuh] /ˈpæt n ə, pəˈti nə/

noun
1.
a film or incrustation, usually green, produced by oxidation on the surface of old bronze and often esteemed as being of ornamental value.
2.
a similar film or coloring appearing gradually on some other substance.
3.
a surface calcification of implements, usually indicating great age.
/ˈpætɪnə/
noun (pl) -nas
1.
a film of oxide formed on the surface of a metal, esp the green oxidation of bronze or copper See also verdigris (sense 1)
2.
any fine layer on a surface: a patina of frost
3.
the sheen on a surface that is caused by much handling
/ˈpætɪnə/
noun (pl) -nae (-ˌniː)
1.
a broad shallow dish used in ancient Rome
n.

“greenish film on old bronze,” 1748, from French patine (18c.), from Italian patina, perhaps from Latin patina “dish, pan” (see pan (n.)), on the notion of encrustation on ancient bronze dishes. Sense of “refinement, cultural sophistication” first recorded 1933.