lethargic vs spring fever

lethargic

adj
  • indifferent, apathetic 

  • sluggish, slow 

spring fever

noun
  • A feeling of invigoration and restlessness associated with the arrival of the warm weather and renewal of nature in the spring season. 

  • A feeling of laziness or listlessness associated with the arrival of the warm, comfortable weather of the spring season. 

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