dullness vs hebetude

dullness

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

  • The quality of not perceiving or kenning things distinctly. 

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

  • Lack of interest or excitement. 

  • The lack of visual brilliance; want of sheen. 

  • bluntness. 

hebetude

noun
  • Mental lethargy or dullness. 

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