Online Etymology Dictionary

implausibility (n.): 1630s, from implausible + -ity.
implausible (adj.): "not having an appearance of truth or credibility," 1670s, from assimilated form of in- "not, opposite of" (see in- (1)) + plausible. Earlier it meant "not worthy of applause" (c. 1600). Related: Implausibly.
implement (n.): mid-15c., "supplementary payment, amount needed to complete repayment," from Late Latin implementem "a filling up" (as with provisions), from Latin implere "to fill, fill up, make full; fatten; fulfill, satisfy," from assimilated form of in- "into, in, on, upon" (see in- (2)) + plere "to fill" (see pleio-). Sense of "workman's tool, utensil of a trade, things necessary to do work" is 1530s. The underlying connection of the senses is "whatever may supply a want, that which fills up a need." Related: Implemental; implements.
implement (v.): "to complete, perform, carry into effect," 1707, originally chiefly in Scottish English, where the noun was a legal term meaning "fulfillment," from implement (n.). It spawned implementation, which is first recorded 1913. Related: Implemented; implementing.
implete (v.): "to fill, pervade," 1862, from Latin impletus, past participle of implere "to fill, fill up" (see implement (n.)). OED says U.S. Related: Impleted; impleting.
impletion (n.): "action of filling," 1580s, from Late Latin impletionem, noun of action from stem of implere "to fill, fill up" (see implement (n.)).
implex (adj.): "intricate, complicated," 1710, from Latin implexus "interwoven, entwined," past participle of implectere. Used by 18c. critics in reference to plots.
implicate (v.): early 15c., "to convey (truth) in a fable," from Latin implicatus, past participle of implicare "to involve, entwine, entangle, embrace" (see implication). From c. 1600 as "intertwine, wreathe." Meaning "involve (someone) in a crime, charge, etc.; show (someone) to be involved" is from 1797. Related: Implicated; implicating.
implication (n.): early 15c., "action of entangling," from Latin implicationem (nominative implicatio) "an interweaving, an entanglement," noun of state from past participle stem of implicare "involve, entangle; embrace; connect closely, associate," from assimilated form of in- "into, in, on, upon" (see in- (2)) + plicare "to fold" (see ply (v.1)). Meaning "that which is implied (but not expressed), inference drawn from what is observed" is from 1550s.
implications (n.): see implication.
implicative (adj.): "tending to implicate," c. 1600, from implicate + -ive. Related: Implicatively (1570s).
implicit (adj.): 1590s, "implied, resting on inference," from Middle French implicite and directly from Latin implicitus, later variant of implicatus "entangled, confused, involved," past participle of implicare "entangle, involve" (see implication). From c. 1600 as "resulting from perfect confidence (in authority), unquestioning" (especially of faith).
implicitly (adv.): c. 1600, "by implication," from implicit + -ly (2). From 1640s as "unquestioningly."
implied (adj.): "intended but not expressed," 1520s, past participle adjective from imply (v.). Implied powers in a constitutional sense is attested from 1784.
implode (v.): 1870 (implied in imploded), back-formation from implosion. Related: Imploding.
implore (v.): c. 1500, from Middle French implorer and directly from Latin implorare "call on for help, beseech, beg earnestly," with a literal sense probably of "plead tearfully, invoke with weeping," from assimilated form of in- "on, upon" (see in- (2)) + plorare "to weep, cry out," a word of unknown origin. Related: Implored; imploring; imploringly; imploration.
implosion (n.): "a bursting inward, a sudden collapse," 1829, modeled on explosion, with assimilated form of in- "into, in, on, upon" (see in- (2)).
And to show how entire the neglect and confusion have been, they speak in the same breath of all these explosions, and of the explosion of a mixture of hydrogen and oxygen, the result of which, instead of being a gas or an enlargement of bulk, a positive quantity, is a negative one. It is a vacuum, in a popular sense, because the produce is water. The result is an implosion (to coin a word), not an explosion .... ["Gas-light," "Westminster Review," October 1829]
In early use often in reference to effect of deep sea pressures, or in phonetics. Figurative sense is by 1960.
implosive (adj.): 1876, originally in linguistics, probably from implode on the model of explosive; implosive is attested in French and German from 1860s.
imply (v.): late 14c., implien, emplien "to enfold, enwrap, entangle" (the classical Latin sense), from Old French emplier, from Latin implicare "involve, enfold, entangle" (see implication). Meaning "to involve something unstated as a logical consequence" first recorded c. 1400; that of "to hint at" is from 1580s. Related: Implied; implying. The distinction between imply and infer is in "What do you imply by that remark?" but, "What am I to infer from that remark?" Or, as Century Dictionary puts it, "An action implies ability or preparation, but involves consequences."
impolite (adj.): 1610s, "unrefined, rough," from Latin impolitus "unpolished, rough, inelegant, unrefined," from assimilated form of in- "not, opposite of" (see in- (1)) + politus "polished" (see polite). Sense of "discourteous, uncivil, unpolished in manners" is from 1739. Related: Impolitely.
impoliteness (n.): 1670s, from impolite + -ness.
impolitic (adj.): "not according to good policy," c. 1600, from assimilated form of in- (1) "not, opposite of" + politic (adj.) "judicious." Related: Impoliticly. Impolicy "quality of being impolitic" is attested from 1747.
imponderable (adj.): 1794, "weightless," from assimilated form of in- (1) "not, opposite of" + ponderable (see ponder). Figurative use, "unthinkable," from 1814. As a noun from 1829, originally meaning heat, light, electricity, etc., as having no weight. Related: Imponderably; imponderability. Imponderous is attested from 1640s as "without weight." Imponderabilia "unthinkable things collectively" is attested from 1835.
import (v.): early 15c., "signify, show, bear or convey in meaning," from Latin importare "bring in, convey, bring in from abroad," from assimilated form of in- "into, in" (see in- (2)) + portare "to carry" (see port (n.1)). In English, the sense of "bring from another state or land," especially "bring in goods from abroad" first recorded 1540s. As "be important" from 1580s. Related: Imported; importing.
import (n.): 1580s, "consequence, importance;" 1680s, "that which is imported;" both from import (v.).
importance (n.): "the quality of having consequence," c. 1500, from Middle French importance or directly from Medieval Latin importantia "importance," from importantem "important" (see important).
important (adj.): mid-15c., from Middle French important and directly from Medieval Latin importantem (nominative importans) "important, momentous," present-participle adjective from importare "be significant in," from Latin importare "bring in" (see import (v.)). Meaning "pretentious, pompous" is from 1713. Related: Importantly.
importation (n.): c. 1600; see import (v.) + -ation.
importer (n.): 1700, agent noun from import (v.).
importunate (adj.): 1520s, from importune + -ate (1), or else from Medieval Latin importunatus, past participle of importunari "to make oneself troublesome." Related: Importunately (mid-15c.). Earlier adjective was importune (c. 1400).
importune (v.): "harass with solicitation, demand persistently," 1520s, back-formation from importunity, or else from Middle French importuner, from Medieval Latin importunari "to make oneself troublesome," from Latin importunus "unfit, unfavorable, troublesome," literally "having no harbor" (thus "difficult to access"), from assimilated form of in- "not, opposite of" (see in- (1)) + portus "harbor" (see port (n.1)). Related: Importuned; importuning. As an adjective from early 15c. Portunus was the Roman deity of harbours; hence Portunium "temple of Portunus."
importunity (n.): "persistence, insistence; over-eagerness," early 15c., from Old French importunité (14c.), from Latin importunitatem (nominative importunitas) "unsuitableness; unmannerliness, unreasonableness, incivility," from importunus "unfit, troublesome" (see importune).
impose (v.): late 14c., "to lay (a crime, duty, obligation, etc.) to the account of," from Old French imposer "put, place; impute, charge, accuse" (c. 1300), from assimilated form of in- "into, in" (see in- (2)) + poser "put, place" (see pose (v.1)). From c. 1500 as "apply authoritatively." Sense of "lay on as a burden, inflict by force or authority" first recorded 1580s. Related: Imposed; imposer; imposing.
imposing (adj.): "impressive in appearance or manner," 1786, present participle adjective from impose (v.). Related: Imposingly.
imposition (n.): late 14c., "a tax, duty, tribute," from Old French imposicion "tax, duty; a fixing" (early 14c.), from Latin impositionem (nominative impositio) "a laying on," noun of action from past participle stem of imponere "to place upon," from assimilated form of in- "into, in" (see in- (2)) + ponere "to put, place" (past participle positus; see position (n.)). Sense of "the act of putting (something) on (something else)" is from 1590s. Meaning "an act or instance of imposing" (on someone) first recorded 1630s (see impose).
impossibilism (n.): "belief in social reforms (or other ideas) that could not practically be attained or accomplished," 1885, from impossible + -ism. Related: Impossibilist.
impossibility (n.): late 14c., "quality of being impossible," from impossible + -ity; perhaps from or modeled on Old French impossibilité (14c.). Meaning "an impossible thing or occurrence" is from c. 1500. Sometimes in English 15c.-18c. it meant "inabolity, impotence," after a use of Medieval Latin impossibilitas.
impossible (adj.): late 14c., from Old French impossible (14c.), from Latin impossibilis "not possible," from assimilated form of in- "not, opposite of" (see in- (1)) + possibilis (see possible). Weakened sense of "unable to be accomplished or tolerated" is from mid-19c. Related: Impossibly.
impost (n.): "tax, duty," 1560s, from Middle French impost (15c., Modern French impôt), from Medieval Latin impostum "a tax imposed," noun use of neuter of Latin impostus, contracted form of impositus, past participle of imponere "to place upon, impose upon" (see impostor). Compare depot. As an architectural term, 1660s, from French imposte (16c.), from Italian imposta, from the same Latin source.
impostor (n.): 1580s, "swindler, cheat," from Middle French imposteur (16c.), from Late Latin impostor "a deceiver," agent noun from impostus, contraction of impositus, past participle of imponere "place upon, impose upon, deceive," from assimilated form of in- "into, in, on, upon" (see in- (2)) + ponere "to put place" (past participle positus; see position (n.)). Meaning "one who passes himself off as another" is from 1620s. Related: Impostrous. For a fem. form, Bacon uses French-based impostress (1610s) while Fuller, the church historian, uses Latinate impostrix (1650s).
imposture (n.): "act of willfully deceiving others," 1530s, from Middle French imposture or directly from Late Latin impostura "deceit," from impostus (see impost (n.)). Related: Imposturous.
impotable (adj.): "undrinkable," c.1600, from assimilated form of in- (1) "not" + potable, or else from Late Latin impotabilis.
impotence (n.): early 15c., "physical weakness," also "poverty," from Old French impotence "weakness" (13c.), from Latin impotentia "lack of control or power," from impotentem "lacking control, powerless" (see impotent). In reference to a complete want of (male) sexual potency, from c. 1500. The figurative senses of the word in Latin were "violence, fury, unbridled passion," via the notion of "want of self-restraining power," and these sometimes were used in English. Related: Impotency.
impotent (adj.): late 14c., "physically weak, enfeebled, crippled," from Old French impotent "powerless, weak, incapable of doing," from Latin imponentem (nominative impotens) "lacking control, powerless, feeble; lacking self-control," from assimilated form of in- "not, opposite of" (see in- (1)) + ponentem (nominative potens) "potent" (see potent).

Meaning "having no power to accomplish anything" is from mid-15c.; that of "completely lacking in sexual power" (of males) is from mid-15c. Middle English also had a native term for this: Cunt-beaten (mid-15c.). The figurative sense in Latin was "without self-control, headstrong, violent, ungovernable, lacking self-restraint," which sometimes is found in English (OED cites examples from Spenser, Massinger, Dryden, and Pope). Related: Impotently.
impound (v.): early 15c., "to shut up in a pen or pound," from assimilated form of in- "into, in" (see in- (2)) + pound (n.). Originally of cattle seized by law. Related: Impounded; impounding.
impoundment (n.): 1660s; see impound + -ment. Earlier in the same sense were impoundage (1610s), impounding (1550s).
impoverish (v.): early 15c., empoverischen, from Old French empoveriss-, stem of empoverir, from em- + povre "poor" (see poor (adj.)). In the same sense Middle English also had empover (early 15c., from Old French enpoverir). Related: Impoverished; impoverishing.
impoverishment (n.): 1550s, from Anglo-French empoverissement, from empoverir; see impoverish + -ment.
impracticable (adj.): "incapable of being done, not to be done by available means," 1670s, from assimilated form of in- (1) "not, opposite of" + practicable. Earlier in a sense of "impassable" (1650s). Related: Impracticably; impracticability.
impractical (adj.): 1823, from assimilated form of in- (1) "not, opposite of" + practical (adj.). Impracticable in the same sense dates from 1670s; unpractical is rare. Related: Impractically.