incentive vs perk

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. 

perk

noun
  • A bonus ability that a player character can acquire; a permanent power-up. 

  • Perquisite. 

  • A percolator, particularly of coffee. 

verb
  • To make trim or smart; to straighten up; to erect; to make a jaunty or saucy display of. 

  • Of coffee: to be produced by heated water seeping (“percolating”) through coffee grounds. 

  • To appear from below or behind something, emerge, pop up, poke out. 

  • To make (coffee) in a percolator or a drip coffeemaker. 

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