night hag vs specter

night hag

noun
  • a demon that gives rise to sleep paralysis 

specter

noun
  • A ghostly apparition, a phantom. 

  • Any of certain species of dragonfly of the genus Boyeria, family Aeshnidae. 

  • A threatening mental image. 

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