prime the pump

As an idiomatic term, from the 1930s. From the metaphor of filling (priming) a liquid pump in order to prepare it for operation.

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prime the pump (third-person singular simple present primes the pump, present participle priming the pump, simple past and past participle primed the pump)

1. (economics) To engage in deficit spending [from 1930s].
   • 1935, Congressional Record, page 4087:

     […] by supplying, through the Federal Treasury, a sufficient flow of finance and currency that will prime the pump and keep it going until it can start its flow from the well or fountain of national resources.

2. To give something in order to create the conditions where others will give in return.
   • 2001, Asa E. Lennon, The Forgotten Self: A Book of Reminders, →ISBN, page 112:

     For example, if you give money to a charity, as a tax reduction or to prime the pump for more money to flow to you, than the actual intent is not making someone else happy, but yourself.

   • 2002, Dana Stabenow, A Fine and Bitter Snow, →ISBN, page 180:

     Kate primed the pump by telling the story of Dina teaching her to rappel.

   • 2011, Dennis Merritt Jones, The Art of Uncertainty: How to Live in the Mystery of Life and Love It, →ISBN:

     A good way to prime the pump of generosity is by starting with the intangibles such as a smile, or a simple courtesy such as opening a door for someone or extending some other random act of kindness.

   • 2012 -, Poppy Smith, Why Can't He Think More Like Me?, →ISBN:

     If you're starving for some admiring comments, you might have to prime the pump.

3. Used other than figuratively or idiomatically: see prime,‎ the,‎ pump.

• pump-prime