foible vs irregularity

foible

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

  • A weakness or failing of character. 

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

irregularity

noun
  • An object or event that is not regular or ordinary. 

  • A violation of rules. 

  • An instance of being irregular. 

  • Irregular bowel movement (e.g. diarrhea or constipation). 

  • The state or condition of being irregular, or the extent to which something is irregular. 

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