How to Memorize

tarnish a reputation, have an untarnished reputation

Analysis

Tarnish is is a discolouration on metals that occurs over time I'm because of oxidation or moisture. When a metal is tarnished, it no longer looks shiny or bright.  If an opinion of somebody is 'tarnished' it means to make somebody or something seem less good. This expression brings to mind a stain on someone's reputation. 

Social Examples (Advance)

1. After the married man had an affair, his reputation was tarnished.
2. Due to his keen understanding of public relations, he managed to emerge from the scandal with an untarnished reputation. 
3. Having lived in the city for so long, it was a joy for Alice to be able to spend some time in the untarnished beauty of the countryside.

Professional Examples (Basic)

1. The attack on our social media has tarnished our reputation immensely.
2. We are specialists in restoring tarnished antiques and silverware.
3. Please remember that while you are abroad you are still representing the university. Be.careful not to behave in a way that might tarnish the University's reputation.

Further Suggestions