ferment vs get at

ferment

verb
  • To stir up, agitate, cause unrest or excitement in. 

  • To react, using fermentation; especially to produce alcohol by aging or by allowing yeast to act on sugars; to brew. 

noun
  • Something, such as a yeast or barm, that causes fermentation. 

  • A gentle internal motion of the constituent parts of a fluid; fermentation. 

  • A state of agitation or of turbulent change. 

  • A catalyst. 

get at

verb
  • To attack verbally or physically; to annoy, bother. 

  • To manage to gain access to. 

  • To understand or ascertain by investigation. 

  • To persuade by intimidation, to tamper with. 

  • To begin working on or dealing with. 

  • To contact someone. 

  • To mean, signify. 

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