hardened vs yielding

hardened

adj
  • Inured; toughened. 

  • Firmly established or unlikely to change; inveterate. 

  • Having extra defences against attack; highly fortified. 

  • Unfeeling; pitiless; callous. 

yielding

noun
  • A concession. 

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

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