ferric vs unbending

ferric

adj
  • Of compounds of iron in which it has a valence or oxidation number of 3 

  • Pertaining to, derived from, or containing iron. 

unbending

adj
  • inflexible and not yielding 

  • very reserved, aloof and asocial 

noun
  • The act of one who unbends. 

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