Use of the phrase "pork barrel" dates back to 1863 and was initially used in reference to any money a government spent on its citizens. This usage was derived from "The Children of the Public," written by Edward Everett Hale. It was not until approximately 10 years later that the phrase and the related concept of pork-barrel politics came to mean spending by a politician specifically done for the benefit of a group of people in exchange for their support. This support usually comes in the form of votes for politicians or money donated to their campaign.

Another possible origin for the phrase "pork barrel" comes from practices prior to the Civil War, in which slave owners would watch their slaves fight each other over a barrel of salted pork given as a reward for services.

Pork barrel spending has negative connotations, particularly within Congress, as it can be seen as a type of bribery, or at the very least a form of influence on the politician. Money and politics often go hand in hand as the cost of mounting an effective political campaign is quite high. However, using general taxpayer funds and increasing overall government spending to benefit one's own constituents as a method of retaining one's office can lead to corruption.

A concept similar to pork-barrel politics is rent-seeking which, while not limited to use by politicians, is often used by them to gain favor with lobbyists and other special-interest groups. Like pork-barrel spending, rent-seeking practices only benefit a very small number of people at the expense of the general taxpaying population.