pertinacious vs yielding

pertinacious

adj
  • Holding tenaciously to an opinion or purpose. 

  • Stubbornly resolute or tenacious. 

yielding

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

noun
  • A concession. 

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