When Italians began using patina in the 17th century to refer to the green film that forms on the surface of copper, they were drawing on Latin, in which patina means "a shallow dish." (Presumably, the Italian meaning developed from the observation of such film forming on copper dishes.) By the mid-18th century, English speakers were also calling the green film patina, and by the 20th century, they'd expanded the word's application to surface appearances of things that have grown more beautiful with age or use—think of an old wooden desk or a tarnished silver goblet. Use of the word to refer to thin layers both literal and figurative ("a patina of grime," "a patina of respectability") followed soon after.