brassy vs iron-hearted

brassy

adj
  • Unfeeling; pitiless. 

  • Impudent; impudently bold. 

  • Harsh in tone. 

  • Resembling brass. 

noun
  • Kyphosus vaigiensis, a fish found in southeast Asia. 

iron-hearted

adj
  • pitiless; inflexibly unsympathetic 

How often have the words brassy and iron-hearted occurred in a corpus of books? (source: Google Ngram Viewer )