Online Etymology Dictionary

immarcessible (adj.): "unfading, imperishable," 1540s, from Late Latin immarcessabilis from assimilated form of in- "not" (see in- (1)) + marcessare "to wither, pine away."
immaterial (adj.): late 14c., "spiritual, incorporeal," from Medieval Latin immaterialis "not consisting of matter, spiritual," from assimilated form of in- "not, opposite of" (see in- (1)) + Late Latin materialis (see material). Secondary sense of "unimportant" is first recorded 1690s from material in its 16c. sense of "important." Related: Immaterially.
immature (adj.): 1540s, "untimely, premature," from Latin immaturus "untimely, unripe," from assimilated form of in- "not, opposite of" (see in- (1)) + maturus (see mature (v.)). In 16c., usually in reference to early death; modern sense of "not fully developed" first recorded 1640s. In reference to mentalities or behaviors not considered age-appropriate, from 1920.
immaturity (n.): 1530s, "untimeliness," from Latin immaturitatem (nominative immaturitas) "unripeness," from immaturus (see immature). Meaning "lack of maturity" attested from c.1600.
immeasurable (adj.): mid-15c., from im- + measurable. It could alternate with immensurable (1530s), from French, from Late Latin immensurabilis, from assimilated form of in- "not" + mensurabilis "able to be measured," from mensurare "to measure." Related: Immeasurably.
immediacy (n.): c.1600, from immediate + -cy.
immediate (adj.): late 14c., "intervening, interposed;" early 15c., "with nothing interposed; direct," also with reference to time, from Old French immediat, from Late Latin immediatus "without anything between," from assimilated form of in- "not, opposite of" (see in- (1)) + mediatus, past participle of mediare "to halve," later, "be in the middle," from Latin medius "middle" (see medial (adj.)).
immediately (adv.): "without intervening time or space," early 15c., from immediate + -ly (2).
immemorable (adj.): 1550s, from Latin immemorabilis, from assimilated form of in- "not" (see in- (1)) + memorabilis (see memorable).
immemorial (adj.): c.1600, from French immémorial (16c.) "old beyond memory," from Medieval Latin immemorialis, from assimilated form of in- "not, opposite of" (see in- (1)) + memorialis (see memorial). Something immemorial is ancient beyond memory; something immemorable is not memorable.
immense (adj.): early 15c., from Middle French immense (mid-14c.), from Latin immensus "immeasurable, boundless," from assimilated form of in- "not, opposite of" (see in- (1)) + mensus "measured," past participle of metiri (see measure).
immensely (adv.): 1650s, from immense + -ly (2).
immensity (n.): mid-15c., from Middle French immensité (14c.) or directly from Latin immensitatem (nominative immensitas) "immeasurableness," noun of quality from immensus (see immense).
immerge (v.): 1620s, "immerse, plunge" (rare), from Latin immergere "to dip, plunge" (see immersion). Related: Immerged; immerging.
immerse (v.): early 15c. (implied in immersed), from Latin immersus, past participle of immergere "to plunge in, dip into" (see immersion). Related: Immersed; immersing; immersive.
immersion (n.): mid-15c., from Late Latin immersionem (nominative immersio), noun of action from past participle stem of immergere, from assimilated form of in- "into, in, on, upon" (see in- (2)) + Latin mergere "plunge, dip" (see merge). Meaning "absorption in some interest or situation" is from 1640s. As a method of teaching a foreign language, it is from 1965, trademarked by the Berlitz company.
immigrant (n.): "one who immigrates," 1792, in an American context, from French immigrant, from Latin immigrantem (nominative immigrans), present participle of immigrare (see immigrate). Emigrant is older. As an adjective from 1805.
immigrate (v.): 1620s, from Latin immigratum, past participle of imigrare "to remove, go into, move in," from assimilated form of in- "into, in, on, upon" (see in- (2)) + migrare "to move" (see migration). Related: Immigrated; immigrating.
immigration (n.): 1650s, from immigrate + -ion. As short for "immigration authorities," from 1966.
imminence (n.): c.1600, from Late Latin imminentia, from Latin imminentem (see imminent).
imminent (adj.): 1520s, from Middle French imminent (14c.) and directly from Latin imminentem (nominative imminens), present participle of imminere "to overhang; impend, be near, be at hand," from assimilated form of in- "into, in, on, upon" (see in- (2)) + minere "jut out," related to mons "hill" (see mount (n.)). Related: Imminently.
immiscible: 1670s, from im- + miscible.
immitigable (adj.): 1570s, from Latin immitigabilis, from assimilated form of in- "not" (see in- (1) + mitigabilis, from past participle stem of mitigare "make mild or gentle" (see mitigate). Related: Immitigably.
immobile (adj.): mid-14c., from Old French immoble "immovable, fixed, motionless," from Latin immobilis "immovable" (also, figuratively, "hard-hearted"), from assimilated form of in- "not, opposite of" (see in- (1)) + mobilis (see mobile (adj.)). Hence, immobilism "policy of extreme conservatism" (1949, from French immobilisme).
immobility (n.): early 15c., from Middle French immobilité (14c.) or directly from Latin immobilitatem (nominative immobilitas), noun of quality from immobilis (see immobile).
immobilization (n.): 1846, noun of action from immobilize.
immobilize (v.): 1843, from immobile + -ize. Cf. French immobiliser (1835). Related: Immobilized; immobilizing.
immoderate (adj.): late 14c., from Latin immoderatus "boundless, immeasurable," figuratively "unrestrained, excessive," from assimilated form of in- "not, opposite of" (see in- (1)) + moderatus "restrained" (see moderate). Related: Immoderately.
immoderation (n.): early 15c., from Latin immoderationem (nominative immoderatio) "want of moderation, excess," from immoderatus (see immoderate).
immodest (adj.): 1560s, "arrogant, impudent, pretentious," from Latin immodestus "unrestrained, excessive," from assimilated form of in- "not, opposite of" (see in- (1)) + modestus (see modest). Meaning "indecent" is from 1580s. Related: immodestly.
immodesty (n.): 1590s, from Latin immodestia "intemperate conduct," from immodestus (see immodest).
immolate (v.): 1540s, "to sacrifice, kill as a victim," from Latin immolatus, past participle of immolare "to sacrifice," originally "to sprinkle with sacrificial meal," from assimilated form of in- "into, in, on, upon" (see in- (2)) + mola (salsa) "(sacrificial) meal," related to molere "to grind" (see mallet). Related: Immolated; immolating.
immolation (n.): early 15c., "a sacrificing" (originally especially with reference to Christ), from Middle French immolation (13c.) or directly from Latin immolationem (nominative immolatio) "a sacrificing," noun of action from past participle stem of immolare (see immolate).
immoral (adj.): 1650s, from assimilated form of in- (1) "not" + moral (adj.). Related: Immorally.
immorality (n.): 1560s, from assimilated form of in- (1) "not, opposite of" + morality.
immortal (adj.): "deathless," late 14c., from Latin immortalis "deathless, undying," from assimilated form of in- "not, opposite of" (see in- (1)) + mortalis "mortal" (see mortal (adj.)). In reference to fame, literature, etc., attested from 1510s (a sense also found in classical Latin). As a noun, from mid-17c.
immortality (n.): mid-14c., "deathlessness," from Old French immortalité (13c.) and directly from Latin immortalitatem (nominative immortalitas) "deathlessness, endless life," from immortalis (see immortal). Sense of "everlasting fame" is from 1530s.
immortalization (n.): c.1600, noun of action or state from immortalize.
immortalize (v.): 1560s, from immortal + -ize. Perhaps modeled on Middle French immortaliser. Related: Immortalized; immortalizing.
immortelle (n.): "flower which preserves its shape and color after being dried," 1832, from French fem. of immortel "undying" (see immortal).
immovability (n.): late 14c.; see immovable + -ity.
immovable (adj.): late 14c., literal and figurative, from assimilated form of in- (1) "not, opposite of" + movable. Related: Immovably.
immune (adj.): mid-15c., "free; exempt," back-formation from immunity. Cf. Latin immunis "exempt from public service, free from taxes." Specific modern medical sense of "exempt from a disease" (typically because of inoculation) is from 1881. Immune system attested by 1917.
immunity (n.): late 14c., "exempt from service or obligation," from Old French immunité and directly from Latin immunitatem (nominative immunitas) "exemption from performing public service or charge," from immunis "exempt, free," from assimilated form of in- "not, opposite of" (see in- (1)) + munis "performing services" (cf. municipal), from PIE *moi-n-es-, suffixed form of root *mei- "to change" (see mutable). Medical sense "protection from disease" is 1879, from French or German.
immunization (n.): 1893, from immunize + -ation.
immunize (v.): 1889, from immune + -ize. Related: Immunized; immunizing.
immunodeficiency: 1969, from comb. form of immune + deficiency.
immunology (n.): by 1906, a hybrid from comb. form of immune + -ology. Related: Immunological; immunologist.
immure (v.): 1580s, from Middle French emmurer and directly from Medieval Latin immurare, literally "to shut up within walls," from assimilated form of in- "into, in" (see in- (2)) + Latin murus "wall" (see mural). Related: Immured; immuring.
immutability (n.): 1590s, from Latin immutabilitas, from immutabilis (see immutable).
Nought may endure but Mutability. [Shelley]