drowsy vs fast asleep

drowsy

adj
  • Inclined to drowse; heavy with sleepiness 

  • Causing someone to fall sleep or feel sleepy; lulling; soporific. 

  • Dull; stupid. 

  • Boring. 

fast asleep

adj
  • Sleeping, in a deep sleep. 

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