prime mover

prime mover idiom
The initial source of energy directed toward a goal, someone or something that sets others in motion. For example, Jean was the prime mover in getting us more laboratory space, or Patriotism was the prime mover of the revolution. [Late 1600s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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