insecurity vs introversion

insecurity

noun
  • A lack of confidence in oneself; self-doubt. 

  • The state of being subject to danger; vulnerability. 

  • A lack of security; uncertainty. 

introversion

noun
  • A personality orientation towards the self and mental abstraction; behavior expressing such orientation. 

  • Arrangement of two similar words, lines, etc. to form the middle part of a structure. 

  • The action of turning one's thoughts upon internal or spiritual matters. 

  • A turning inward 

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