discarding vs expungement

discarding

noun
  • The act by which something is discarded; a throwing away. 

  • Discarded material. 

expungement

noun
  • The act of expunging. 

  • The process by which the record of a criminal conviction is erased, destroyed or sealed. 

How often have the words discarding and expungement occurred in a corpus of books? (source: Google Ngram Viewer )