insecurity vs instability

insecurity

noun
  • The state of being subject to danger; vulnerability. 

  • A lack of security; uncertainty. 

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

instability

noun
  • The quality of being unstable. 

  • A state that is not in equilibrium, or in which a small change has a large irreversible effect. 

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