In thermodynamics, impelling power is synonym for the term motive power, used in 1824 by French engineer Sadi Carnot, which can be understood in modern terms as work or the resultant effect of a weight being lifted through a height. [1]

Etymology
The term “impelling power” dates back to at least the 16th century, as it is found in the works of English scientist Francis Bacon. In one instance Bacon states: “the effects produced by gunpowder, are occasioned by the impelling power being quicker than the power of resistance.” [2] According to a more recent 1914 definition, which seems fairly straight forward, impelling power is a force that pushes or impels per unit time. [3]

References
1. Carnot, Sadi. (1824). “Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power.” Paris: Chez Bachelier, Libraire, Quai Des Augustins, No. 55.
2. Bacon, Francis. (1825). The Works of Francis Bacon (pg. 501). W. Pickering.
3. Dorland, William. (1914). Dorland’s illustrated Medical Dictionary (pg. 1048). W.B. Saunders Co.