combustive vs incentive

combustive

adj
  • Of, pertaining to, caused by, or partaking in combustion. 

incentive

adj
  • Serving to kindle or set on fire. 

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

noun
  • Something that motivates, rouses, or encourages. 

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

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