asleep vs hypnagogic

asleep

adj
  • In a state of sleep; also, broadly, resting. 

  • Inattentive. 

  • Having a numb or prickling sensation accompanied by a degree of unresponsiveness. 

  • Dead. 

hypnagogic

adj
  • That accompanies falling asleep; especially, pertaining to the semi-conscious period immediately preceding sleep. 

  • That induces sleep; soporific, somniferous. 

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