emaciate vs rarefy

emaciate

verb
  • To make extremely thin or wasted. 

  • To become extremely thin or wasted. 

adj
  • emaciated 

rarefy

verb
  • To make rare, thin, porous, or less dense 

  • To expand or enlarge without adding any new portion of matter to. 

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