immutable (adj.)
early 15c., from Old French immutable and directly from Latin immutabilis "unchangeable," from assimilated form of in- "not, opposite of" (see in- (1)) + mutabilis "changeable," from mutare "to change" (see mutable). Related: Immutably.
imp (n.)
Old English impe, impa "young shoot, graft," from impian "to graft," probably an early West Germanic borrowing from Vulgar Latin *imptus, from Late Latin impotus "implanted," from Greek emphytos, verbal adjective formed from emphyein "implant," from em- "in" + phyein "to plant" (see physic).

Sense of "child, offspring" (late 14c.) came from transfer of word from plants to people, with notion of "newness" preserved. Modern meaning "little devil" (1580s) is from common use in pejorative phrases like imp of Satan.
Suche appereth as aungelles, but in very dede they be ymps of serpentes. ["The Pilgrimage of Perfection," 1526]
impact (v.)
c.1600, "press closely into something," from Latin impactus, past participle of impingere "to push into, dash against, thrust at" (see impinge). Originally sense preserved in impacted teeth (1876). Sense of "strike forcefully against something" first recorded 1916. Figurative sense of "have a forceful effect on" is from 1935. Related: Impacting.
impact (n.)
1781, "collision," from impact (v.). Figurative sense of "forceful impression" is from 1817 (Coleridge).
impactful (adj.)
1968, from impact + -ful. Related: Impactfully; impactfulness.
impaction (n.)
1739, from Latin impactionem (nominative impactio) "a striking against," noun of action from past participle stem of impingere (see impinge).
impair (v.)
late 14c., earlier ampayre, apeyre (c.1300), from Old French empeirier (Modern French empirer), from Vulgar Latin *impeiorare "make worse," from assimilated form of in- "into, in" (see in- (2)) + Late Latin peiorare "make worse" (see pejorative). In reference to driving under the influence of alcohol, first recorded 1951 in Canadian English. Related: Impaired; impairing.
impairment (n.)
mid-14c., emparement, from Old French empeirement, from empeirier (see impair). Re-Latinized spelling is from 1610s.
impala (n.)
1875, from Zulu im-pala "gazelle."
impale (v.)
1520s, "to enclose with stakes, fence in," from Middle French empaler and directly from Medieval Latin impalare "to push onto a stake," from assimilated form of in- "into, in" (see in- (2)) + Latin palus "a stake, prop, stay; wooden post, pole," from PIE *pak-slo-, from root *pag-/*pak- "to fasten" (see pact). Sense of "pierce with a pointed stake" (as torture or punishment) first recorded 1610s. Related: Impaled; impaling.
impalement (n.)
1590s, from French empalement, from empaler (see impale).
impalpable (adj.)
c.1500, from French impalpable, from Medieval Latin impalpabilis, from assimilated form of in- "not, opposite of" (see in- (1)) + palpabilis (see palpable). Figurative use from 1774. Related: Impalpably; impalpability.
impanate (adj.)
"present in the (consecrated) bread," 1540s, from Church Latin impanatus, past participle of impanare "to embody in bread," from assmiliated form of in- "in, into" (see in- (2)) + panis "bread" (see food).
impart (v.)
early 15c., "to give a part of (one's possessions); late 15c., "to share, take part," from Old French impartir (14c.), from Late Latin impartire (also impertire) "to share in, divide with another, communicate," from assimilated form of in- "into, in" (see in- (2)) + partire "to divide, part" (see part (v.)). Related: Imparted; imparting.
impartial (adj.)
formed in English 1590s from assimilated form of in- (1) "not, opposite of" + partial. First recorded in "Richard II."
impartiality (n.)
1610s; see impartial + -ity.
impassable (adj.)
"that cannot be passed," 1560s, from im- + passable.
impasse (n.)
1851, "blind alley," from French impasse "impassable road, blind alley, impasse," from assimilated form of in- "not, opposite of" (see in- (1)) + Middle French passe "a passing," from passer "to pass" (see pass (v.)). Supposedly coined by Voltaire as a euphemism for cul de sac. Figurative use also from 1851.
impassible (adj.)
"incapable of feeling pain, exempt from suffering," mid-14c., from Old French impassible (13c.), from Church Latin impassibilis "incapable of passion," from assimilated form of in- "not, opposite of" (see in- (1)) + passibilis, from passio "suffering" (see passion). Related: Impassibility.
impassion (v.)
1590s, from Italian impassionare "to fill with passion," from im- "in, into" (see im-) + passione "passion," from Latin passionem (see passion). Related: Impassioned.
impassionate (adj.)
"free from passion," 1620s, from in- (1) "not" + passionate. Related: Impassionately.
impassioned (adj.)
c.1600, past participle adjective from impassion.
impassive (adj.)
1660s, "not feeling pain," from assimilated form of in- "not, opposite of" (see in- (1)) + passive. Meaning "void of emotions" is from 1690s. Related: Impassively; impassiveness (1640s).
impassivity (n.)
1794, from impassive + -ity.
impasto (n.)
laying on of colors thickly," 1784, from Italian impasto, noun of action from impastare "to raise paste; to put in paste," from assimilated form of in- "into, in" (see in- (2)) + pasta "paste" (see pasta).
impatience (n.)
c.1200, from Old French impacience (Modern French impatience) and directly from Latin impatientia, from impatiens (see impatient).
impatient (adj.)
late 14c., from Old French impacient (Modern French impatient), from Latin impatientem (nominative impatiens) "that cannot bear, intolerant, impatient," from assimilated form of in- "not, opposite of" (see in- (1)) + patiens (see patience). Related: Impatiently.
impeach (v.)
late 14c., "to impede, hinder, prevent," from Anglo-French empecher, Old French empeechier "hinder" (12c., Modern French empêcher), from Late Latin impedicare "to fetter, catch, entangle," from assimilated form of in- "into, in" (see in- (2)) + Latin pedica "shackle," from pes (genitive pedis) "foot." Sense of "accuse a public officer of misconduct" first recorded 1560s, perhaps via confusion with Latin impetere "attack, accuse." Related: Impeached; impeaching.
impeachable (adj.)
c.1500, from impeach + -able. Related: impeachably; impeachability.
impeachment (n.)
late 14c., enpechement "accusation, charge," from Old French empechement, from empeechier (see impeach). As a judicial proceeding against a public official, from 1640s.
impeccable (adj.)
1530s, "not capable of sin," from Middle French impeccable (15c.) or directly from Late Latin impeccabilis "not liable to sin," from assimilated form of in- "not, opposite of" (see in- (1)) + pecare "to sin," of unknown origin. Meaning "faultless" is from 1610s. Related: Impeccably.
impecunious (adj.)
"lacking in money," 1590s, from assimilated form of in- "not, opposite of" (see in- (1)) + Latin pecuniosus "rich," from pecunia "money, property" (see pecuniary). Related: Impecuniously; impecuniosity.
impedance (n.)
1886, from impede + -ance.
impede (v.)
c.1600, back-formation from impediment, or else from Latin impedire "impede, be in the way, hinder, detain," literally "to shackle the feet" (see impediment). Related: Impeded; impedes; impeding.
impediment (n.)
c.1400, from Latin impedimentem "hindrance," from impedire "impede," literally "to shackle the feet," from assimilated form of in- "into, in" (see in- (2)) + pes (genitive pedis) "foot" (see foot (n.)).
impedimenta (n.)
"traveling equipment," c.1600, from Latin impedimenta "luggage, baggage," literally "that by which one is impeded;" plural of impedimentum (see impediment).
impel (v.)
early 15c., from Latin impellere "to push, strike against, drive forward, urge on," from assimilated form of in- "into, in, on, upon" (see in- (2)) + pellere "to push, drive" (see pulse (n.1)). Related: Impelled; impelling.
impeller (n.)
1680s, agent noun from impel (v.). As a machine part from 1890.
impend (v.)
1590s, from figurative use of Latin impendere "to hang over, to be imminent," from assimilated form of in- "into, in, on, upon" (see in- (2)) + pendere "hang" (see pendant). Related: Impended; impending.
impendent
1590s, from Latin impendens "impending," present participle of impendere (see impend).
impenetrable (adj.)
mid-15c., from Middle French impenetrable, from Latin impenetrabilis "that cannot be penetrated," from assimilated form of in- "not, opposite of" (see in- (1)) + penetrabilis "penetrable" (see penetrate). Related: Impenetrably; impenetrability.
impenitence (n.)
1620s, from Latin impaenitentia, from impaenitens (see impenitent). Impenitency is from 1560s.
impenitent (adj.)
early 15c., from Latin impaenitentem, from assimilated form of in- "not, opposite of" (see in- (1)) + paenitens (see penitence).
imperative (adj.)
1520s, from Late Latin imperativus "pertaining to a command," from imperatus "commanded," past participle of imperare "to command, to requisition," from assimilated form of in- "into, in" (see in- (2)) + parare "prepare" (see pare).
imperative (n.)
mid-15c., in grammar; later "something imperative" (c.1600), from Old French imperatif and directly from Late Latin imperativus (see imperative (adj.)).
imperator (n.)
"commander-in-chief," Latin agent noun from stem of imperare "to command" (see imperative). In the Roman republic, a commander; in the Roman Empire, the emperor.
imperceptibility (n.)
1670s, from imperceptible + -ity.
imperceptible (adj.)
early 15c., from French imperceptible (early 15c.), from Medieval Latin imperceptibilis, from assimilated form of in- "not, opposite of" (see in- (1)) + perceptibilis (see perceptible). Related: Imperceptibly. OED marks imperceivable as "Now rare."
imperfect (adj.)
mid-14c., imperfite, from Old French imparfait, from Latin imperfectus "unfinished, incomplete," from assimilated form of in- "not, opposite of" (see in- (1)) + perfectus (see perfect). Replaced mid-16c. by the Latin form. Related: Imperfectly.
imperfection (n.)
late 14c., from Old French imperfeccion (12c.) and directly from Late Latin imperfectionem (nominative imperfectio), from imperfectus (see imperfect).