bravery vs mettle

bravery

noun
  • Being brave, courageousness. 

  • A brave act. 

  • Splendor, magnificence. 

mettle

noun
  • A quality of endurance and courage. 

  • Good temperament and character. 

adj
  • Spirited, vigorous, stout-hearted. 

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