tarnish \tar"nish\, v. t. imp.  p. p. tarnished; p. pr. 
   vb. n. tarnishing. f. ternir, fr. ohg. tarnen to darken,
   to conceal, hide; akin to os. dernian to hide, as. dernan,
   dyrnan, ohg. tarni hidden, os. derni, as. derne, dyrne. cf.
   dern, a., and see -ish.
   to soil, or change the appearance of, especially by an
   alternation induced by the air, or by dust, or the like; to
   diminish, dull, or destroy the luster of; to sully; as, to
   tarnish a metal; to tarnish gilding; to tarnish the purity of
   color. "tarnished lace." --fuller. used also figuratively;
   as, to tarnish one's honor.
   1913 webster

   syn: to sully; stain; dim.
        1913 webster
see also:
tarnished tarnishing dern -ish