incentive vs payback

incentive

noun
  • A bonus or reward, often monetary, to work harder. 

  • Something that motivates, rouses, or encourages. 

adj
  • Inciting; encouraging or moving; rousing to action; stimulating. 

  • Serving to kindle or set on fire. 

payback

noun
  • A benefit, reward, a form of recompense. 

  • An act of revenge. 

  • A return on investment. 

  • A refund; reimbursement. 

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