repayment vs slush fund

repayment

noun
  • The money or other item that is repaid. 

  • The act of revenge, an act of revenge. 

  • The act of repaying. 

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. 

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