reflux vs retract

reflux

verb
  • To flow back or return. 

  • To boil a liquid in a vessel having a reflux condenser 

noun
  • A technique, using a reflux condenser, allowing one to boil the contents of a vessel over an extended period. 

  • The backwards flow of any fluid. 

  • The leaking of stomach acid up into the oesophagus. 

retract

verb
  • To pull (something) back or back inside. 

  • To avert (one's eyes or a gaze). 

  • To decline or fail to do something promised; to break one's word. 

  • Of something said or written (such as published academic work): to take back or withdraw. 

  • To draw (an extended body part) back into the body. 

  • To take back or withdraw (something that has been said or written); to disavow, to repudiate. 

  • Originally in chess and now in other games as well: to take back or undo (a move); specifically (card games) to take back or withdraw (a card which has been played). 

  • To break or fail to keep (a promise, etc.); to renege. 

  • To draw back; to draw up; to withdraw. 

  • To pronounce (a sound, especially a vowel) farther to the back of the vocal tract. 

  • To cancel or take back (something, such as an edict or a favour or grant previously bestowed); to rescind, to revoke. 

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