certitude vs firmness

certitude

noun
  • Sureness, certainty. 

  • Something that is a certainty. 

firmness

noun
  • security; steadfastness; good grip 

  • strictness; mental strength 

  • physical durability; rigidness (of material) 

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