mettle vs powerlessness

mettle

noun
  • Good temperament and character. 

  • A quality of endurance and courage. 

adj
  • Spirited, vigorous, stout-hearted. 

powerlessness

noun
  • The state or character of being powerless; absence or lack of power. 

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