precious stone, a blue-to-transparent variety of corundum next in hardness to diamond, mid-13c., saphyr, from Old French saphir (12c.) and directly from Latin sapphirus (source also of Spanish zafir, Italian zaffiro), from Greek sappheiros, name of a blue precious stone, from a Semitic source (compare Hebrew sappir "sapphire"), but according to OED probably not ultimately from Semitic.
Some linguists propose an origin in Sanskrit sanipriya, a dark precious stone (perhaps sapphire or emerald), literally "sacred to Saturn," from Sani "Saturn" + priyah "precious." The gem meant by the Greeks apparently was not the one now so called, but perhaps rather lapis lazuli, the modern sapphire perhaps being signified by Greek hyakinthos. In Renaissance lapidaries, it was said to cure anger and stupidity. As an adjective from early 15c. As a color, a deep brilliant or bright blue, by 1680s. Related: Sapphiric.