divergence vs fluctuation

divergence

noun
  • The degree to which two or more things diverge. 

  • The process in which two or more populations accumulate genetic changes (mutations) through time. 

  • the operator which maps a function F=(F₁, ... Fₙ) from a n-dimensional vector space to itself to the function ∑ᵢ₌₁ⁿ(∂F_i)/(∂x_i) 

fluctuation

noun
  • A wavering; unsteadiness. 

  • In medicine, a wave-like motion or undulation of a fluid in a natural or abnormal cavity (e.g. pus in an abscess), which is felt during palpation or percussion. 

  • A motion like that of waves; a moving in this and that direction. 

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