fidelity vs stab in the back

fidelity

noun
  • Accuracy, or exact correspondence to some given quality or fact. 

  • Faithfulness to one's duties. 

  • Loyalty to one's spouse or partner, including abstention from cheating or extramarital affairs. 

  • The degree to which a system accurately reproduces an input. 

stab in the back

verb
  • To betray (somebody). 

noun
  • An act of betrayal or treachery 

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