incentive vs income

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. 

income

noun
  • Money one earns by working or by capitalising on the work of others. 

  • A disease or ailment without known or apparent cause, as distinguished from one induced by accident or contagion; an oncome. 

  • That which is taken into the body as food; the ingesta; sometimes restricted to the nutritive, or digestible, portion of the food. 

  • Money coming in to a fund, account, or policy. 

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