1680s as the name of a type of steel-gray metal, from German kobold "household goblin" (13c.), which became also a Harz Mountains silver miners' term for rock laced with arsenic and sulfur (according to OED so called because it degraded the ore and made the miners ill), from Middle High German kobe "hut, shed" + *holt "goblin," from hold "gracious, friendly," a euphemistic word for a troublesome being.
The metallic element (closely resembling nickel but much rarer) was extracted from this rock. It was known to Paracelsus, but discovery is usually credited to the Swede George Brandt (1733), who gave it the name. Extended to a blue color 1835 (a mineral containing it had been used as a blue coloring for glass since 16c.). Compare nickel. Related: Cobaltic; cobaltous.
early 14c., "a devil, incubus, mischievous and ugly fairy," from Norman French gobelin (12c., as Medieval Latin Gobelinus, the name of a spirit haunting the region of Evreux, in chronicle of Ordericus Vitalis), of uncertain origin; said to be unrelated to German kobold (see cobalt), or from Medieval Latin cabalus, from Greek kobalos "impudent rogue, knave," kobaloi "wicked spirits invoked by rogues," of unknown origin. Another suggestion is that it is a diminutive of the proper name Gobel.
Though French gobelin was not recorded until almost 250 years after appearance of the English term, it is mentioned in the Medieval Latin text of the 1100's, and few people who believed in folk magic used Medieval Latin. [Barnhart]
Thou schalt not drede of an arowe fliynge in the dai, of a gobelyn goynge in derknessis [Psalms xci.5 in the later Wycliffe Bible, late 14c.]