exhaustion vs somnolence

exhaustion

noun
  • Supreme tiredness; having exhausted energy. 

  • An exhaustive procedure 

  • The point of complete depletion, of the state of being used up. 

somnolence

noun
  • A state of drowsiness or sleepiness. 

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