American Dictionary of the English Language

CAMEO, CAMAIEU OR CAMAYEU, noun A peculiar sort of onyx; also, a stone on which are found various figures and representations of landscapes, a kind of lusus naturae, exhibiting pictures without painting. The word is said to be the oriental camehuia, a name given to the onyx, when they find, in preparing it, another color; as who should say, another color.