to dull the lustre of (something) by, or as if by, dirt, air, etc, or be dulled in this way
to mar or spoil or be spoiled (something)
to bring discredit on or be discredited (e.g. a person's reputation)
to become tarnished
tarnishable adj
[Middle English from early French ternir, from terne dark, dull, of Germanic origin]