foible vs unsadness

foible

noun
  • A weakness or failing of character. 

  • A quirk, idiosyncrasy, or mannerism; an unusual habit that is slightly strange or silly. 

  • Part of a sword between the middle and the point, weaker than the forte. 

unsadness

noun
  • infirmity, unsteadiness, weakness 

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