ineptness vs mettle

ineptness

noun
  • The quality or degree of being inept. 

mettle

noun
  • Good temperament and character. 

  • A quality of endurance and courage. 

adj
  • Spirited, vigorous, stout-hearted. 

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