impulse (n.)

early 15c., "an act of impelling, a thrust, push," from Latin impulsus "a push against, pressure, shock," figuratively "incitement, instigation," past participle of impellere "to strike against, push against," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + pellere "to push, drive" (from PIE root *pel- (5) "to thrust, strike, drive"). Meaning "a stimulus in the mind to action, arising from some state or feeling" is first recorded 1640s. As an adjective, in reference to purchases made on impulse, 1955 (in impulse buyer).