the.com/tarnish
What air does to silver and gossip does to reputations: a slow dulling.
means To lose shine or be discolored by chemical reaction, or to damage someone's good name.
from From French ternir, to make dim, rooted in a word for dull or wan — the look of metal forgetting how to gleam.
ChemistrySilver tarnish is sulfur from the air bonding on.
Not rustTarnish is surface film; rust eats deeper.
Reputation useFigurative sense dulls honor as readily as metal.