What's the origin of "slush fund"?
Dear Straight Dope:
Where did the term "slush fund" come from and how do I get one?
In olden days, like the early 1800s, fried salt pork was a staple food aboard ships. At the end of a voyage, the grease at the bottom of the pork barrel, called "slush," was sold to candle and soap makers. The money usually helped provide little extras that the crew couldn't otherwise afford, hence the term "slush fund." After the U.S. Civil War, the term was applied to a contingency fund set aside by Congress, outside of the regular operating budget, that was often used for bribes and other corrupt purposes. .
By the way, the term "pork-barrel," referring to the federally-funded projects of dubious necessity that members of Congress use to reward loyal constituents, is probably derived from the same origin.
Although the term tends to have a negative connotation, slush funds aren't necessarily shady or illegal. For example, a group of business partners may set up an unallocated fund that they can draw on to cover business-related expenses for which the company otherwise has no specific reimbursement policy. I was in such a situation myself, and could use my share of that fairly small fund for any business-related, tax-deductible purpose not covered under some other budget line-item--for example, taking employees out for a celebratory lunch. The fund was formally called a "Partner Reimbursable Account," but informally it was our slush fund.
Dictionary of Word and Phrase Origins, William and Mary Morris (1962)
When a Loose Cannon Flogs a Dead Horse, There's the Devil to Pay, Olivia A. Isil (1996)