E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
a natural cameo, or intaglio. These stones (chiefly agate) contain natural representations of plants, landscapes, or animals. Pliny tells us that the Agate of Pyrrhus contained a representation of the nine Muses, with Apollo in the midst. Paracelsus calls them natural talismans. Albertus Magnus makes mention of them, and Gaffaret, in his Curiosités inouïes, attributes to them magical powers. (French, camaïeu, from the oriental gamahuia, camehuia, or camebouia.)
When magic was ranked as a science, certain conjunctions were called Gamahæan unions.