boldness vs mettle

boldness

noun
  • The state of being bold; courage. 

  • The relative weight of a font; the thickness of its strokes. 

  • presumptuousness 

mettle

noun
  • A quality of endurance and courage. 

  • Good temperament and character. 

adj
  • Spirited, vigorous, stout-hearted. 

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