refractory vs yielding

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. 

yielding

noun
  • A concession. 

adj
  • Docile, or inclined to give way to pressure. 

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