severing vs undoing

severing

noun
  • The act by which something is severed. 

undoing

noun
  • The act of loosening or unfastening 

  • Annulment; reversal 

  • Ruin; defeat, (also) that which causes defeat or ruin. 

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