birdbrain vs undead

birdbrain

noun
  • Someone who is not intelligent. 

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 birdbrain and undead occurred in a corpus of books? (source: Google Ngram Viewer )