lethargy vs pep

lethargy

noun
  • A condition characterized by extreme fatigue or drowsiness, deep unresponsiveness, or prolonged sleep patterns. 

  • A state of extreme torpor or apathy, especially with lack of emotion, energy or enthusiasm; (loosely) sluggishness, laziness. 

pep

verb
  • To inject with energy and enthusiasm. 

noun
  • Energy, high spirits. 

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