backlash vs ferment

backlash

verb
  • To cause or set off a backlash. 

noun
  • A sudden backward motion. 

  • A negative reaction, objection or outcry, especially of a violent or abrupt nature. 

  • The jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion. 

  • The looseness through which one part of connected machinery, as a wheel, gear, piston, or screw, can be moved without moving the connected parts, or a measurement of the distance moved thereby; either intentional (as allowance) or unintentional (from error or wear). 

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. 

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