cumshaw vs pourboire

cumshaw

noun
  • A gratuity or tip as thanks for a service 

verb
  • To give or make a present to. 

pourboire

noun
  • A tip (extra money given to e.g. a waiter in appreciation of service), especially in French contexts. 

  • A bribe. 

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