bravery vs firmness

bravery

noun
  • Being brave, courageousness. 

  • A brave act. 

  • Splendor, magnificence. 

firmness

noun
  • strictness; mental strength 

  • security; steadfastness; good grip 

  • physical durability; rigidness (of material) 

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