comshaw vs gratuity

comshaw

noun
  • A bribe or gratuity for a service or for arranging a deal; squeeze. 

  • The practice of pilfering or bartering for surplus items. 

verb
  • To acquire without officially requisitioning; to pilfer or barter for surplus items. 

gratuity

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

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