slush fund vs tribute

slush fund

noun
  • Money stored for illegal or dishonest purposes. 

  • Money that has not been hypothecated or dedicated to a particular purpose, or which is used for a different purpose than originally intended. 

tribute

noun
  • Extortion; protection money. 

  • A certain proportion of the mined ore, or of its value, given to the miner as payment. 

  • A payment made by one nation to another in submission. 

  • An homage made in a body of work to another work or creator. 

  • An acknowledgment of gratitude, respect or admiration; an accompanying gift. 

  • A payment made by a feudal vassal to his lord. 

verb
  • To pay as tribute. 

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