From late 17th c. Middle Russian крушецъ, кружецъ (krušec, kružec, “metallic ore; metal, product of its smelting; mine”), from Old Ruthenian крушецъ (krušecʹ, “ore, useful mineral; metal, product of ore smelting”) (since 1566), from Middle Polish kruszec, Polish kruszcz, from Old Polish kruszec (“ore, useful mineral, especially rock salt”) (since 1472; cf. Polish kruch (“unit of measurement of salt; salt stone”)), from Old Czech krušec (“lump of a useful mineral, especially rock salt”), krušek, from kruch (“piece, chunk”), from Proto-Slavic *kruxъ, from Proto-Balto-Slavic *kraušas, from Proto-Indo-European *krows-o-s, ultimately from *krews- (“to freeze, become hard”).
Promoted by purists as an alternative to металл (metall) but fell out of use by 1830s.
круше́ц • (krušéc) m inan (genitive крушца́, nominative plural крушцы́, genitive plural крушцо́в)