incubus vs night hag

incubus

noun
  • A feeling of oppression during sleep, sleep paralysis; night terrors, a nightmare. 

  • An evil spirit supposed to oppress people while asleep, especially to have sex with women as they sleep. 

  • Any oppressive thing or person; a burden. 

  • One of various of parasitic insects, especially subfamily Aphidiinae. 

night hag

noun
  • a demon that gives rise to sleep paralysis 

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