disperse vs peter out

disperse

verb
  • To disseminate. 

  • To break up and disappear; to dissipate. 

  • To scatter in different directions. 

  • To separate rays of light, etc., according to wavelength; to refract. 

  • To distribute throughout. 

adj
  • Scattered or spread out. 

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”) 

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