Origin of slush fund
Examples from the Web for slush fund
Plunder-bund is now at least as good as pork-barrel and slush-fund, and money-bund is frequently heard in Congress.The American Language|Henry L. Mencken
A collection of money by a political official or administration that is used to make payments for various services. Though slush funds may be used for legitimate purposes, such as paying state employees, the term is generally used to describe money that is not properly accounted for and is being used for personal expenses and political payoffs. Money raised for political campaigns has come under increasing public scrutiny to ensure that it is not misused.