ductile vs unyielding

ductile

adj
  • Led easily; prone to follow. 

  • Capable of being pulled or stretched into thin wire by mechanical force without breaking. 

  • Molded easily into a new form. 

unyielding

adj
  • Not giving in; not bending; stubborn. 

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