lackadaisical vs stonehearted

lackadaisical

adj
  • Lazy; slothful; indolent. 

  • Showing no interest, vigor, determination, or enthusiasm. 

stonehearted

adj
  • Hardhearted; pitiless; unfeeling. 

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