ghoul vs undead

ghoul

noun
  • A demon said to feed on corpses. 

  • A person with a callous or uncaring attitude to human life and suffering, particularly when prioritising economic concerns. 

  • A person with an undue interest in death and corpses, or more generally in things that are revolting and repulsive. 

  • A graverobber. 

undead

noun
  • A creature that is undead; that is, dead but still animate. 

  • Those creatures which are undead; that is, dead yet still animate. 

adj
  • Being animate, though non-living. 

  • Pertaining to a corpse, though having qualities of life. 

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