backset vs recurrence

backset

noun
  • A check; a relapse; a discouragement; a setback. 

  • Whatever is thrown back in its course, such as water. 

verb
  • To plow again in the fall; said of prairie land broken up in the spring. 

recurrence

noun
  • Recourse. 

  • The instance of recurring; frequent occurrence. 

  • A return of symptoms as part of the natural progress of a disease. 

  • Return or reversion to a certain state. 

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