The manufacture of untarnishable gold for embroidery purposes seems beyond present day enterprise.
It was said to be untarnishable and unstainable even when used with the strongest acid foods, as well as non-rusting.
1590s, from present participle stem of Middle French ternir "dull the luster or brightness of, make dim" (15c.), probably from Old French terne (adj.) "dull, dark," from a Germanic source cognate with Old High German tarnjan "to conceal, hide," Old English dyrnan "to hide, darken," from Proto-Germanic *darnjaz (see dern). Figurative sense is from 1690s. Related: Tarnished; tarnishing.
1713, from tarnish (v.).