fealty vs unfaithfulness

fealty

noun
  • Fidelity to one's lord or master; the feudal obligation by which the tenant or vassal was bound to be faithful to his lord. 

  • The oath by which this obligation was assumed. 

unfaithfulness

noun
  • The characteristic of being unfaithful; infidelity; disloyalty. 

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