Know how to use "fewer" and "less"? Find out.
early 15c., "driving, pushing, thrusting," from Old French impulsion (early 14c.), from Latin impulsionem (nominative impulsio) "external pressure," figuratively "incitement, instigation," noun of action from past participle stem of impellere (see impel).
impulsion im·pul·sion (ĭm-pŭl'shən)
An urge to perform certain actions without regard for internal or social constraints.