early 15c., from Latin impellere "to push, strike against; set in motion, drive forward, urge on," 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"). Related: Impelled; impelling.

1680s, agent noun from impel (v.). As a machine part from 1836.

early 15c., "a driving, pushing, thrusting," from Old French impulsion (14c.), from Latin impulsionem (nominative impulsio) "external pressure," figuratively "incitement, instigation," noun of action from past participle stem of impellere (see impel).

early 15c., originally in reference to medicine that reduces swelling or humors, from Medieval Latin impulsivus, from Latin impuls-, past participle stem of impellere "strike against, push against" (see impel). Meaning "having the property of impelling" (of force, cause, energy, etc.) is from c. 1600. Of persons, "rash, characterized by impulses," from 1847, from impulse. Earlier, at least once, in reference to maniacs:

The impulsive insane are often irritable, restless and jealous. Sometimes they have delusions, and sometimes not. Their delusions frequently seem to have no connection with their outbreaks of violence. They are often the best and at the same time the most dangerous class of patients in the asylums. They have little of the charity of the world, are most likely to be punished for their offences, and yet have the least control over their conduct. ["Impulsive and Homicidal Insanity," Boston Medical and Surgical Journal, April 19, 1843]

Proto-Indo-European root meaning "to thrust, strike, drive."

It forms all or part of: anvil; appeal; catapult; compel; dispel; expel; felt (n.) "unwoven fabric matted together by rolling or beating;" filter; filtrate; impel; impulse; interpellation; interpolate; peal; pelt (v.) "to strike (with something);" polish; propel; pulsate; pulsation; pulse (n.1) "a throb, a beat;" push; rappel; repeal; repel; repousse.

It is the hypothetical source of/evidence for its existence is provided by: Greek pallein "to wield, brandish, swing," pelemizein "to shake, cause to tremble;" Latin pellere "to push, drive;" Old Church Slavonic plŭstĭ.

1640s, from Latin instinct-, past participle stem of instinguere "to incite, impel" (see instinct) + -ive. Related: Instinctively (1610s); instinctiveness. Coleridge uses instinctivity.

early 15c., via Medieval Latin, from Greek enema "injection," from enienai "to send in, inject," from en "in" (from PIE root *en "in") + hienai "to send, throw" (from PIE root *ye- "to throw, impel").

1590s, from Latin subiacentem (nominative subiacens) "lying beneath," present participle of subiacere "to lie underneath, lie near, adjoin," from sub "under," also "close to" (see sub-) + iacere "to throw" (from PIE root *ye- "to throw, impel").

1590s, from Latin interiacentem (nominative interiacens) "lying between," present participle of interiacere "to lie between," from inter "among, between" (see inter-) + iacere "to throw; to set, establish" (from PIE root *ye- "to throw, impel"). Related: Interjacency.

1570s, "emit semen," from Latin eiaculatus, past participle of eiaculari "to throw out, shoot out," from ex "out" (see ex-) + iaculari "to throw, hurl, cast, dart," from iaculum "javelin, dart," from iacere "to throw" (from PIE root *ye- "to throw, impel"). Sense of "exclaim suddenly" is from 1660s. Related: Ejaculated; ejaculating; ejaculatory.