deathly vs mortiferous

deathly

adj
  • Deadly, fatal, causing death. 

  • Extreme. 

  • Appearing as though dead, or on the verge of death. 

adv
  • In a way that resembles death. 

  • Extremely, dreadfully. 

mortiferous

adj
  • Causing physical death; deadly, fatal, lethal. 

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