obdurate vs stonehearted

obdurate

adj
  • Hardened against feeling; hard-hearted. 

  • Stubbornly persistent, generally in wrongdoing; refusing to reform or repent. 

stonehearted

adj
  • Hardhearted; pitiless; unfeeling. 

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