instability vs oscillation

instability

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

  • The quality of being unstable. 

oscillation

noun
  • the act of oscillating or the state of being oscillated 

  • (of a function) defined for each point x in the domain of the function by inf diam(f(U))∣Uisaneighborhoodofx, and describes the difference (possibly ∞) between the limit superior and limit inferior of the function near that point. 

  • a single such cycle 

  • a regular periodic fluctuation in value about some mean 

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