firmness vs sureness

firmness

noun
  • strictness; mental strength 

  • security; steadfastness; good grip 

  • physical durability; rigidness (of material) 

sureness

noun
  • The property of being sure, deft, confident of ability. 

  • The property of being sure, certainty. 

  • The result or product of being sure. 

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