pliable vs unyielding

pliable

adj
  • Easily persuaded; yielding to influence. 

  • Soft, flexible, easily bent, formed, shaped, or molded. 

unyielding

adj
  • Not giving in; not bending; stubborn. 

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