peter out vs vanish into thin air

peter out

verb
  • Synonym of peter (“originally (mining), of a vein of ore: to be depleted of ore; now (generally), to diminish to nothing; to dwindle, to trail off”) 

vanish into thin air

verb
  • To disappear in a mysterious way. 

How often have the words peter out and vanish into thin air occurred in a corpus of books? (source: Google Ngram Viewer )