baksheesh vs gratuity

baksheesh

verb
  • To bribe with a baksheesh. 

noun
  • in the Middle East, southwest Asia and Eastern Europe: a bribe or tip. 

  • A minor wound that is severe enough to get a soldier sent away from the front. 

gratuity

noun
  • An additional payment given freely as thanks for service. 

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