incentive vs red rag to a bull

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. 

red rag to a bull

noun
  • Something that will enrage another particular person. 

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