conceited vs diffident

conceited

adj
  • Having an excessively favorable opinion of one's abilities, appearance, etc.; vain and egotistical. 

  • Having an ingenious expression or metaphorical idea, especially in extended form or used as a literary or rhetorical device. 

diffident

adj
  • Lacking self-confidence; timid; modest 

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