Online Etymology Dictionary

intimate (adj.): 1630s, "closely acquainted, very familiar," from Late Latin intimatus, past participle of intimare "make known, announce, impress," from Latin intimus "inmost" (adj.), "close friend" (n.), superlative of in "in" (see in- (2)). Used euphemistically in reference to women's underwear from 1904. Related: Intimately.
intimate (v.): "suggest indirectly," 1530s, back-formation from intimation, or else from Late Latin intimatus, past participle of intimare. Related: Intimated; intimating.
intimate (n.): 1650s, "person with whom one is intimate," from intimate (adj.).
intimation (n.): mid-15c., "action of making known," from Middle French intimation (late 14c.), from Late Latin intimationem (nominative intimatio) "an announcement" (in Medieval Latin "a judicial notification"), noun of action from past participle stem of intimare (see intimate). Meaning "suggestion, hint" is from 1530s.
intimidate (v.): 1640s, from Medieval Latin intimidatus, past participle of intimidare "to frighten, intimidate," from Latin in- "in" (see in- (2)) + timidus "fearful" (see timid). Related: Intimidated; intimidating.
intimidation (n.): 1650s, noun of action from intimidate; perhaps modeled on French intimidation.
into: Old English into, originally in to. The word is a late Old English development to replace the fading dative case inflections that formerly distinguished, for instance, "in the house" from "into the house." To be into something, "be intensely involved in," first recorded 1969 in American English.
intolerability (n.): 1590s, from Late Latin intolerabilitas, from Latin intolerabilis (see intolerable).
intolerable (adj.): late 14c., from Latin intolerabilis "that cannot bear, that cannot be borne," from in- "not, opposite of" (see in- (1)) + tolerabilis "that may be endured," from tolerare "to tolerate" (see toleration). Related: Intolerably.
intolerance (n.): "unwillingness to endure a differing opinion," 1765, from Latin intolerantia "impatience, unendurableness, insufferableness, insolence," from intolerantem (see intolerant). Especially of religious matters through mid-19c. Now-obsolete intolerancy was used in same sense from 1620s.
intolerant (adj.): 1735, from Latin intolerantem (nominative intolerans) "not enduring, impatient, intolerant; intolerable," from in- “not” (see in- (1)) + tolerans, present participle of tolerare “to bear, endure” (see toleration). Of plants, from 1898. The noun meaning "intolerant person or persons" is from 1765.
intonate (v.): 1795, from Medieval Latin intonatus, past participle of intonare (see intone) + -ate (2). Cf. Italian intonare, French entonner. Related: Intonated; intonating.
intonation (n.): 1610s, "opening phrase of a melody," from French intonation, from Medieval Latin intonationem (nominative intonatio), from past participle stem of intonare (see intone). Meaning "modulation of the voice in speaking" is from 1791.
intone (v.): late 14c., entunen "sing, chant, recite," from Old French entoner "sing, chant" (13c.), from Medieval Latin intonare "sing according to tone," from Latin in- "in" (see in- (2)) + tonus "tone," from Greek tonos (see tenet). A different verb intone was in use 17c.18c., from Latin intonare "to thunder, resound," figuratively "to cry out vehemently," from tonare "to thunder." Related: Intoned; intoning.
intoxicant (n.): "liquor," 1863; see intoxicate.
intoxicate (v.): "to poison," mid-15c., from Medieval Latin intoxicatus, past participle of intoxicare "to poison," from Latin in- "in" (see in- (2)) + toxicare "to poison," from toxicum "poison" (see toxic). Meaning "make drunk" first recorded 1570s. Related: Intoxicated; intoxicating.
intoxicated (adj.): 1550s, "poisoned;" 1570s, "drunk," past participle adjective from intoxicate (v.).
intoxication (n.): c.1400, intoxigacion "poisoning," from Medieval Latin intoxicationem (nominative intoxicatio) "poisoning," noun of action from past participle stem of intoxicare (see intoxicate). Meaning "drunkenness" is from 1640s.
intra-: word-forming element meaning "within, inside, on the inside," from Latin intra "on the inside, within," related to inter "between," from PIE *en-t(e)ro-, from root *en "in" (see in). Commonly opposed to extra-, but the use of intra as a prefix was rare in classical Latin.
intracellular (adj.): 1876, from intra- + cellular.
intractability (n.): 1570s, from intractable + -ity.
intractable (adj.): c.1500, "rough, stormy;" 1540s, "not manageable," from Latin intractabilis "not to be handled, unmanageable," from in- "not, opposite of" (see in- (1)) + tractabilis (see tractable). Related: Intractably.
intramural (adj.): 1846, literally "within the walls," from intra- "within" + Latin muralis "pertaining to a wall," from murus "wall" (see mural). Activity "within the walls" of a city, building, community, school, etc. Equivalent to Late Latin intramuranus.
intramuscular (adj.): 1874, from intra- + muscular.
intransigence (n.): 1882, from French intransigeant, from intransigeant (see intransigent). Related: Intransigency.
intransigent (adj.): 1881, from French intransigeant, from Spanish los intransigentes, literally "those not coming to agreement," name for extreme republican party in the Spanish Cortes 1873-4, from in- "not" (see in- (1)) + transigente "compromising," from Latin transigentem (nominative transigens), present participle of transigere "come to an agreement, accomplish, to carry through" (see transaction). Acquired its generalized sense in French.
intransitive (adj.): 1610s, from Late Latin intransitivus "not passing over" (to another person), Priscian's term, from Latin in- "not" (see in- (1)) + transitivus "that may pass over," from transire "to pass over" (see transitive).
intraocular (adj.): 1826, from intra- + ocular.
intraperitoneal (adj.): 1835, from intra- + peritoneal.
intrapersonal (adj.): also intra-personal, 1853, from intra- + personal.
intrapsychic (adj.): 1917, from intra- + psychic.
intravenous (adj.): 1847, coined in English from intra- "within, inside" + Latin venous, from vena "vein" (see vein). Related: Intravenously.
intrepid (adj.): 1620s (implied in intrepidness), from French intrépide (16c.) and directly from Latin intrepidus "unshaken, undaunted," from in- "not" (see in- (1)) + trepidus "alarmed" (see trepidation). Related: Intrepidly.
intrepidity (n.): 1704, from intrepid + -ity.
intricacy (n.): c.1600, from intricate + -acy.
intricate (adj.): early 15c., from Latin intricatus "entangled," past participle of intricare "to entangle, perplex, embarrass," from in- "in" (see in- (2)) + tricae (plural) "perplexities, hindrances, toys, tricks," of uncertain origin (cf. extricate). Related: Intricately.
intrigante (n.): "women given to intrigue," 1806, from fem. of French intrigant, from Italian intrigante, present participle of intrigare (see intrigue).
intrigue (v.): 1610s, "to trick, deceive, cheat" (earlier entriken, late 14c.), from French intriguer (16c.), from Italian intrigare "to plot, meddle," from Latin intricare "entangle" (see intricate). Meaning "to plot or scheme" first recorded 1714; that of "to excite curiosity" is from 1894. Related: Intrigued; intriguing (1680s, "plotting, scheming;" meaning "exciting curiosity" is from 1909).
intrigue (n.): 1640s, probably from intrigue (v.).
intrinsic: late 15c., "interior, inward, internal," from Middle French intrinsèque "inner" (13c.), from Medieval Latin intrinsecus "interior, internal," from Latin intrinsecus (adv.) "inwardly, on the inside," from intra "within" (see intra-) + secus "alongside," originally "following" (related to sequi "to follow;" see sequel). Meaning "belonging to the nature of a thing" is from 1640s. Related: Intrinsicly.
intro: short for introduction, attested from 1923.
intro-: word-forming element, from Latin intro "on the inside, within, to the inside," from PIE *en-t(e)ro-, suffixed form of preposition *en "in" (see in).
introduce (v.): early 15c., back-formation from introduction, or else from Latin introducere "to lead in, bring in" (see introduction). Related: Introduced; introducing.
introduction (n.): late 14c., "act of bringing into existence," from Old French introduccion and directly from Latin introductionem (nominative introductio) "a leading in," noun of action from past participle stem of introducere "to lead in, bring in, to introduce," from intro- "inward, to the inside" (see intro-) + ducere "to lead" (see duke (n.)). Meaning "initial instruction in a subject; an introductory statement" is mid-15c. The sense of "formal presentation of one person to another" is from 1711.
introductory (adj.): c.1600, from Late Latin introductorius, from introduct-, past participle stem of introducere "to lead in, bring in" (see introduction). Also used in English from c.1400 as a noun meaning "introductory treatise or textbook."
introit (n.): late 15c., from Old French introit (14c.), from Latin introitus "a going in," past participle of introire "to enter," from intro- (see intro-) + ire "to go" (see ion).
introject (v.): 1925, probably a back-formation from introjection. Related: Introjected; introjecting.
introjection (n.): 1866, from intro- + stem abstracted from projection. In philosophical and psychoanalytical use, from German introjektion.
intron: 1978, from intragenic + -on.
introspect (v.): 1680s, from Latin introspectus, past participle of introspicere "look at, look into" (see introspection). Related: Introspected; introspecting.