intolerability (n.) Look up intolerability at Dictionary.com
1590s, from intolerable + -ity or else from Late Latin intolerabilitas, from Latin intolerabilis "that cannot bear; that cannot be borne." Slightly earlier in the same sense was intolerableness.
intolerable (adj.) Look up intolerable at Dictionary.com
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 bear, endure" (see toleration). Related: Intolerably.
intolerance (n.) Look up intolerance at Dictionary.com
1765, "unwillingness to endure a differing opinion or belief," from Latin intolerantia "impatience; unendurableness, insufferableness; insolence," from intolerantem "impatient, intolerant" (see intolerant). There is an isolated use from c. 1500, with an apparent sense of "unwillingness." Especially of religious matters through mid-19c. Now-obsolete intolerancy was used in same sense from 1620s; intoleration from 1610s. Meaning "incapacity to bear or endure" is by 1844.
intolerant (adj.) Look up intolerant at Dictionary.com
1735, "unable or unwilling to endure" (a condition, etc.), 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).

Meaning "not disposed to endure contrary opinions or beliefs, impatient of dissent or opposition" is from 1765. Of plants, with reference to deep shade, from 1898. The noun meaning "person or persons who do not favor toleration" is from 1765. Related: Intolerantly.
intonate (v.2) Look up intonate at Dictionary.com
"to thunder, rumble," 1620s, from past participle stem of Latin intonare "to thunder, thunder forth," from in- (see in (2)) + tonare "to thunder" (see thunder (n.)). Related: Intonated; intonating.
intonate (v.1) Look up intonate at Dictionary.com
"to intone, recite in a singing voice," 1795, from Medieval Latin intonatus, past participle of intonare "sing according to tone" (see intone). Compare Italian intonare, French entonner. Related: Intonated; intonating.
intonation (n.) Look up intonation at Dictionary.com
1610s, "opening phrase of a melody," from French intonation (14c.), from Medieval Latin intonationem (nominative intonatio), noun of state from past participle stem of intonare (see intone). From 1788 as "action of intoning." Meaning "modulation of the voice in speaking, utterance of tones" is from 1791.
intone (v.2) Look up intone at Dictionary.com
obsolete 17c.-18c. verb, from French entoner "thunder, roar, resound, reverberate," from Latin intonare "to thunder, resound," figuratively "to cry out vehemently," from tonare "to thunder" (see thunder (n.)). Related: Intoned; intoning.
intone (v.1) Look up intone at Dictionary.com
late 14c., entunen "sing, chant, recite, vocalize," from Old French entoner "to 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). Related: Intoned; intoning.
intoxicant (n.) Look up intoxicant at Dictionary.com
"that which intoxicates," 1863; see intoxicate. Perhaps from Medieval Latin intoxicantem (nominative intoxicans), present participle of intoxicare. As an adjective from 1882.
intoxicate (v.) Look up intoxicate at Dictionary.com
mid-15c., "to poison" (obsolete), from Medieval Latin intoxicatus, past participle of intoxicare "to poison," from in- "in" (see in- (2)) + Latin toxicare "to poison," from toxicum "poison" (see toxic). Meaning "make drunk" first recorded 1570s (implied in intoxicated). Figurative sense "excite to a high pitch of feeling" is attested from 1590s. Related: Intoxicating.
intoxicated (adj.) Look up intoxicated at Dictionary.com
1550s, "poisoned;" 1570s, "drunk," past participle adjective from intoxicate (v.).
intoxication (n.) Look up intoxication at Dictionary.com
c. 1400, intoxigacion "poisoning, administration of poison," from Medieval Latin intoxicationem (nominative intoxicatio) "a poisoning," noun of action from past participle stem of intoxicare "to poison" (see intoxicate). Meaning "state of inebriation" is from 1640s.
intra- Look up intra- at Dictionary.com
word-forming element meaning "within, inside, on the inside," from Latin preposition intra "on the inside, within, in, into;" of time, "during, in the course of," related to inter "between," from PIE *en-t(e)ro-, from root *en "in" (see in). Commonly opposed to extra-, and compare inter-. The use of intra as a prefix was rare in classical Latin.
intra-orbital (adj.) Look up intra-orbital at Dictionary.com
also intraorbital, 1887, from intra- "within" + orbit (n.) + -al (1).
intra-uterine (adj.) Look up intra-uterine at Dictionary.com
1835; see intra- "within" + uterine.
intracellular (adj.) Look up intracellular at Dictionary.com
also intra-cellular, "existing or happening inside a cell," 1876; see intra- "within" + cellular.
intractability (n.) Look up intractability at Dictionary.com
1570s, from intractable + -ity. Intractableness is from 1660s.
intractable (adj.) Look up intractable at Dictionary.com
c. 1500, "rough, stormy;" 1540s, "not manageable," from French intractable (15c.) or directly from Latin intractabilis "not to be handled, unmanageable," from in- "not, opposite of" (see in- (1)) + tractabilis (see tractable). Related: Intractably.
intragenic (adj.) Look up intragenic at Dictionary.com
also intra-genic, "occurring within a gene," 1937, from intra- "within" + gene + -ic.
intramercurial (adj.) Look up intramercurial at Dictionary.com
"being within the orbit of the planet Mercury," 1859, especially in reference to a supposed planet orbiting there (sought in vain in the eclipse of 1860), from intra- "within, inside" + Mercury (Latin Mercurius) + -al (1). The idea originated in France in the 1840s with Urbain Le Verrier, who later became director of the Paris Observatory. There was some excitement about it in 1859 when a French doctor named Lescarbault claimed to have tracked it crossing the Sun's disk and convinced Le Verrier. It was sought in vain in the solar eclipses of 1860, '68, and '69. See Vulcan.
intramural (adj.) Look up intramural at Dictionary.com
1846, literally "within the walls, being within the walls or boundaries" (of a city, building, etc.), 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.) Look up intramuscular at Dictionary.com
also intra-muscular, 1874, from intra- "within" + muscle (Latin musculus) + -ar.
intrans. Look up intrans. at Dictionary.com
abbreviation of intransitive (adj.).
intransigence (n.) Look up intransigence at Dictionary.com
1874, from intransigent or else from or based on French intransigeance, from intransigent. Related: Intransigency (1883).
intransigent (adj.) Look up intransigent at Dictionary.com
1874, "uncompromising, refusing to agree or come to understanding," (used of extreme political factions or parties), from French intransigeant (18c.), from Spanish los intransigentes, literally "those not coming to agreement," name for extreme left in the Spanish Cortes and the extreme republicans of the 1870s, 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). It acquired its generalized sense in French. As a noun in English from 1879.
intransitive (adj.) Look up intransitive at Dictionary.com
1610s, from Late Latin intransitivus "not transitive, not passing over" (to another person), Priscian's term, from in- "not" (see in- (1)) + Latin transitivus "that may pass over," from transire "to pass over" (see transitive). The noun meaning "an intransitive verb" is attested from 1824.
intranslatable (adj.) Look up intranslatable at Dictionary.com
1680s, from in- (1) "not, opposite of" + translate + -able. Related: Itranslatably; intranslatability.
intranslatable (adj.) Look up intranslatable at Dictionary.com
1680s, from in- (1) "not, opposite of" + translate + -able. Related: Itranslatably; intranslatability.
intransmissible (adj.) Look up intransmissible at Dictionary.com
1650s, from in- (1) "not, opposite of" + transmissible. Related: Intransmissibly; intransmissibility.
intransmutable (adj.) Look up intransmutable at Dictionary.com
1690s, from in- (1) "not, opposite of" + transmute (v.) + -able). Related: Intransmutably; intransmutability.
intraocular (adj.) Look up intraocular at Dictionary.com
1826, from intra- + ocular.
intraperitoneal (adj.) Look up intraperitoneal at Dictionary.com
also intra-peritoneal, "within the cavity of the peritoeum," 1835, from intra- "within" + peritoneal.
intrapersonal (adj.) Look up intrapersonal at Dictionary.com
also intra-personal, 1853, from intra- "within" + personal.
intrapsychic (adj.) Look up intrapsychic at Dictionary.com
1917, from intra- "within" + psychic.
intraspecific (adj.) Look up intraspecific at Dictionary.com
1905, from intra- + specific, here representing species (n.).
intravenous (adj.) Look up intravenous at Dictionary.com
"in or occurring within a vein," 1847, from intra- "within, inside" + Latin venous, from vena "vein" (see vein). Related: Intravenously.
intrench (v.) Look up intrench at Dictionary.com
obsolete form of entrench (q.v.). Related: Intrenched; intrenchment.
intrepid (adj.) Look up intrepid at Dictionary.com
"unmoved by danger, undaunted," 1690s, from French intrépide (16c.) and directly from Latin intrepidus "unshaken, undaunted, not alarmed," from in- "not" (see in- (1)) + trepidus "alarmed," from PIE *trep-(1) "to tremble" (see trepidation). Related: Intrepidly; intrepidness (1620s).
intrepidity (n.) Look up intrepidity at Dictionary.com
1704, from intrepid + -ity.
intricacy (n.) Look up intricacy at Dictionary.com
c. 1600, "state of being complex;" 1610s, "an intricate situation or condition," from intricate (adj.) + -cy. Related: Intricacies.
intricate (adj.) Look up intricate at Dictionary.com
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," a word of uncertain origin (compare extricate). Related: Intricately; intricateness.
intrigant (n.) Look up intrigant at Dictionary.com
also intriguant, "man given to intrigue," 1781, from French intrigant "male intriguer," from Italian intrigante, noun use of present participle of intrigare "to plot, meddle" (see intrigue (v.)).
intrigante (n.) Look up intrigante at Dictionary.com
also intriguante, "woman given to intrigue," 1806, from fem. of French intrigant "male intriguer," from Italian intrigante, noun use of present participle of intrigare "to plot, meddle" (see intrigue (v.)).
intrigue (n.) Look up intrigue at Dictionary.com
1640s, "a clandestine plot;" 1660s, "secret plotting," probably from intrigue (v.). Also used from 1660s as "clandestine or illicit sexual encounter."
intrigue (v.) Look up intrigue at Dictionary.com
1610s, "to trick, deceive, cheat," from French intriguer (16c.), from Italian intrigare "to plot, meddle; perplex, puzzle," from Latin intricare "to entangle, perplex, embarrass" (see intricate).

Meaning "to plot or scheme" first recorded 1714. That of "to excite curiosity" is from 1894 (OED calls this use "A modern gallicism"). It also could mean "carry on a clandestine or illicit sexual relationship" (1650s). The word appears earlier in English as entriken "entangle, ensnare; involve in perplexity, embarrass" (late 14c.), from Old French entrique or directly from the Latin verb. Related: Intrigued; intriguer; intriguing. Dutch intrigueren, German intriguiren are from French.
intriguing (adj.) Look up intriguing at Dictionary.com
1680s, "plotting, scheming," present-participle adjective from intrigue (v.). Meaning "exciting curiosity" is from 1909. Related: Intriguingly.
intrinsic (adj.) Look up intrinsic at Dictionary.com
late 15c., "interior, inward, internal," from Middle French intrinsèque "inner" (14c.), from Medieval Latin intrinsecus "interior, internal," from Latin intrinsecus (adv.) "inwardly, on the inside," from intra "within" (see intra-) + secus "along, alongside," from PIE *sekw-os- "following," suffixed form of root *sekw- (1) "to follow" (see sequel).

The form in English was conformed to words in -ic by 18c. Meaning "belonging to the nature of a thing" is from 1640s. Related: Intrinsical; intrinsically.
intro (n.) Look up intro at Dictionary.com
short for introduction, attested from 1923.
intro- Look up intro- at Dictionary.com
word-forming element, from Latin intro (adv.) "in, on the inside, within, to the inside," from PIE *en-t(e)ro-, suffixed form of preposition *en "in" (see in).