hard as iron vs intense

hard as iron

adj
  • very hard 

intense

adj
  • Stressful and tiring. 

  • Extreme in size or strength. 

  • Strained; tightly drawn. 

  • Extreme in degree; excessive. 

  • Very severe. 

  • Very emotional or passionate. 

  • Strict, very close or earnest. 

How often have the words hard as iron and intense occurred in a corpus of books? (source: Google Ngram Viewer )