stiffness vs untreatability

stiffness

noun
  • inflexibility or a measure of inflexibility. 

  • inelegance; a lack of relaxedness. 

  • rigidity or a measure of rigidity. 

  • muscular tension due to unaccustomed or excessive exercise or work; soreness. 

untreatability

noun
  • The state or condition of being untreatable. 

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