late 14c., "the direction east; the part of the horizon where the sun first appears," also (now with capital O-) "the eastern regions of the world, eastern countries" (originally vaguely meaning the region east and south of Europe, what is now called the Middle East but also sometimes Egypt and India), from Old French orient "east" (11c.), from Latin orientem (nominative oriens) "the rising sun, the east, part of the sky where the sun rises," originally "rising" (adj.), present participle of oriri "to rise" (see origin).
Meaning "a pearl of the first water" is by 1831, short for pearl of the Orient (late 14c.) originally meaning one from the Indian seas. Hence also the meaning "a delicate iridescence, the peculiar luster of a fine pearl" (1755). The Orient Express was a train that ran from Paris to Istanbul via Vienna 1883-1961, from the start it was associated with espionage and intrigue.
"precious metal noted for its color, luster, malleability, and freedom from rust or tarnish," Old English gold, from Proto-Germanic *gulthan "gold" (source also of Old Saxon, Old Frisian, Old High German gold, German Gold, Middle Dutch gout, Dutch goud, Old Norse gull, Danish guld, Gothic gulþ), from PIE root *ghel- (2) "to shine," with derivatives denoting gold (the "bright" metal).
The root is the general Indo-European one for "gold," found in Germanic, Balto-Slavic (compare Old Church Slavonic zlato, Russian zoloto, "gold"), and Indo-Iranian. Finnish kulta is from German; Hungarian izlot is from Slavic. For Latin aurum see aureate. Greek khrysos probably is from Semitic.
From Homer on through Middle English, "red" often is given as a characteristic color of pure gold or objects made from it. This is puzzling, but it might stem from an ancient practice of testing the purity of gold by heating it; in Middle English red gold was "pure gold" (c. 1200).
Nay, even more than this, the oftener gold is subjected to the action of fire, the more refined in quality it becomes; indeed, fire is one test of its goodness, as, when submitted to intense heat, gold ought to assume a similar colour, and turn red and igneous in appearance; a mode of testing which is known as "obrussa." [Pliny, "Natural History," 33.19]