fealty vs reliability

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. 

reliability

noun
  • The quality of being reliable, dependable, or trustworthy. 

  • the ability to measure the same thing consistently (of a measurement indicating the degree to which the measure is consistent); that is, repeated measurements would give the same result (See also validity). 

  • measurable time of work before failure 

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