dread vs perturbation

dread

noun
  • Reverential or respectful fear; awe. 

  • A Rastafarian. 

  • Great fear in view of impending evil; fearful apprehension of danger; anticipatory terror. 

  • Somebody or something dreaded. 

verb
  • To be in dread, or great fear. 

  • To style (the hair) into dreadlocks. 

  • To fear greatly. 

  • To anticipate with fear. 

adj
  • Terrible; greatly feared; dreaded. 

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 dread and perturbation occurred in a corpus of books? (source: Google Ngram Viewer )