incentive vs rationale

incentive

noun
  • Something that motivates, rouses, or encourages. 

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

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

  • Serving to kindle or set on fire. 

rationale

noun
  • A justification or rationalization for something. 

  • An explanation of the basis or fundamental reasons for something. 

  • A liturgical vestment worn by some Christian bishops of various denominations. 

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