excitability vs perturbation

excitability

noun
  • The state of being excitable 

  • A measure of how easy something is to excite 

perturbation

noun
  • Agitation; the state of being perturbed 

  • Variation in an orbit due to the influence of external bodies 

  • A small change in a physical system, or more broadly any definable system (such as a biological or economic system) 

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