dullness vs somnolence

dullness

noun
  • Lack of interest or excitement. 

  • The quality of not perceiving or kenning things distinctly. 

  • The quality of being uninteresting; boring; humorless or irksome. 

  • The quality of being slow of understanding things; stupidity. 

  • The lack of visual brilliance; want of sheen. 

  • bluntness. 

somnolence

noun
  • A state of drowsiness or sleepiness. 

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