ferrous vs unbending

ferrous

adj
  • Of or containing iron. 

  • Of compounds of iron in which it has a valence or oxidation number of 2. 

unbending

adj
  • inflexible and not yielding 

  • very reserved, aloof and asocial 

noun
  • The act of one who unbends. 

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