firmness vs laxity

firmness

noun
  • strictness; mental strength 

  • security; steadfastness; good grip 

  • physical durability; rigidness (of material) 

laxity

noun
  • Moral looseness; lack of rigorousness or strictness. 

  • The state of being lax; looseness, lack of tension. 

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