refractory vs weak-willed

refractory

noun
  • A material or piece of material, such as a brick, that has a very high melting point. 

adj
  • Obstinate and unruly; strongly opposed to something. 

  • Not affected by great heat. 

  • Difficult to treat. 

  • Incapable of registering a reaction or stimulus. 

weak-willed

adj
  • irresolute, indecisive 

  • easily swayed 

How often have the words refractory and weak-willed occurred in a corpus of books? (source: Google Ngram Viewer )