Encourage the growth or action of something, as in Marjorie tried to prime the pump by offering some new issues for discussion. In the late 1800s this expression originally was used for pouring liquid into a pump to expel the air and make it work. In the 1930s it was applied to government efforts to stimulate the economy and thereafter was applied to other undertakings. (http://www.answers.com/topic/prime-the-pump)