hard as iron vs torrid

hard as iron

adj
  • very hard 

torrid

adj
  • Full of difficulty. 

  • Full of intense emotions arising from sexual love; ardent and passionate. 

  • [of a streak, form, etc.] Good, impressive, hot 

  • Very hot and dry. 

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