Online Etymology Dictionary

intergenerational (adj.): 1964, from inter- + generation + -al (1).
interglacial (adj.): 1867 in reference to warm spells between ice ages, from German, coined 1865 by Swiss naturalist Oswald Heer (1809-1883); see inter- "between" + glacial. The word was used earlier in reference to situations between glaciers or ice caps (1835).
interim (n.): "time intervening," 1560s, from Latin interim (adv.) "in the meantime, meanwhile," originally "in the midst of that," from inter- "between" (see inter-) + im, ancient adverb from stem of pronoun is "this, that." As an adjective from c. 1600.
interior (adj.): late 15c., from Latin interior "inner, interior, middle," comparative adjective of inter "within" (see inter-). Specific meaning "away from the coast, of the interior parts of a country" is from 1777. Interior decoration first attested 1769; interior decorator is from 1830. Interior design from 1927.
interior (n.): "part of a country distant from the coast," 1796, from interior (adj.); meaning "internal part, inside" is from 1828. Meaning "internal affairs of a country or state" (as in U.S. Department of the Interior) is from 1826. The Latin adjective also was used as a noun.
interiority (n.): 1701, from interior + -ity.
interjacent (adj.): 1590s, from Latin interiacentem (nominative interiacens) "lying between," present participle of interiacere "to lie between," from inter- (see inter-) + iacere "to throw; to set, establish" (see jet (v.)). Related: Interjacency.
interject (v.): 1570s, back-formation from interjection or else from Latin interiectus, past participle of intericere "to throw between, insert, interject." Related: Interjected; interjecting.
interjection (n.): early 15c., "an interjected or exclamatory word," from Middle French interjection (Old French interjeccion, 13c.), from Latin interiectionem (nominative interiectio) "a throwing or placing between," also in grammar and rhetoric, noun of action from past participle stem of intericere "to throw between, set between," from inter- "between" (see inter-) + -icere, comb. form of iacere "to throw" (see jet (v.)). Related: Interjectional.
interlace (v.): formerly also enterlace, late 14c. (trans.), "unite by crossing the laces," thus, "entangle, bind together," from Old French entrelacier (12c.), from entre- (see entre-) "between" + lacier "to tie, entangle," from laz (see lace (n.)).

Intransitive sense from 1590s. Television sense is from 1927. Related: Interlaced; interlacing; interlacement. The noun is 1904, from the verb.
interlanguage (n.): "artificial or auxilliary language," 1927, from inter- + language.
interlard (v.): early 15c., "to mix with alternate layers of fat" (before cooking), from Old French entrelarder (12c.), from entre- "between" (see inter-) + larder "to lard," from Old French lard "bacon fat" (see lard (n.)). Figurative sense of "diversify with something intermixed" first recorded 1560s. Related: Interlarded; interlarding; interlardment.
interleaf (n.): "extra page in a book," usually left blank and for taking notes, 1741, from inter- "between" + leaf (n.).
interleague (adj.): also inter-league, by 1917 in a U.S. baseball sense, from inter- "between" + league (n.). Earlier (1580s) as a verb, "to combine in a league."
interline (v.): c. 1400, "make corrections or insertions between the lines of (a document)," from inter- "between" + line; perhaps modeled on Old French entreligniere or Medieval Latin interlineare "write between lines." Related: Interlined; interlining; interlineation.
interlinear (adj.): late 14c., "situated between the lines," from Medieval Latin interlinearis "that which is between the lines," from inter- (see inter-) "between" + Latin linearis (see linear). Meaning "having interpolated lines" is from 1620s. Related: Interlineary.
interlingual (adj.): "between or relating to two languages," 1854, from inter- "between" + lingual. Related: Interlingually.
interlock (v.): 1630s, "to be locked together," from inter- "between" + lock (v.). Related: Interlocked; interlocking. As a noun, attested by 1856.
interlocution (n.): "interchange of speech, dialogue, action of talking and replying," 1530s, from Latin interlocutionem (nominative interlocutio) "a speaking between, interlocution," noun of action from past participle stem of interloqui "to speak between; to interrupt" (see interlocutor).
interlocutor (n.): 1510s, "one who speaks in a dialogue or conversation," agent noun from Latin interlocut-, past participle stem of interloqui "speak between; interrupt," from inter- "between" (see inter-) + loqui "to speak" (see locution).

In minstrel shows, the name of a straight-man character (1870) who was the questioner of the end men. Related: Interlocutory. Fem. forms include interlocutress (1858), interlocutrix (1846), interlocutrice (1848).
interlope (v.): "intrude where one has no business," especially with a view to gain the advantage or profits of another (as a trader without a proper licence), early 17c., probably a back-formation from interloper (q.v.). Related: Interloped; interloping.
interloper (n.): 1590s, enterloper, "unauthorized trader trespassing on privileges of chartered companies," probably a hybrid from inter- "between" + -loper (from landloper "vagabond, adventurer," also, according to Johnson, "a term of reproach used by seamen of those who pass their lives on shore"); perhaps from a dialectal form of leap, or from Middle Dutch loper "runner, rover," from lopen "to run," from Proto-Germanic *hlaupan "to leap" (see leap (v.)).

OED says Dutch enterlooper "a coasting vessel; a smuggler" is later than the English word and said by Dutch sources to be from English. General sense of "self-interested intruder" is from 1630s.
interlude (n.): formerly also enterlude, c. 1300, from Old French entrelude and directly from Medieval Latin interludium "an interlude," from Latin inter "between" (see inter-) + ludus "a play" (see ludicrous). Originally the term for farcical episodes drawn from real life introduced between acts of long mystery plays. In 17c.-18c. it meant "popular stage play;" transferred (non-dramatic) sense of "interval in the course of some action" is from 1751. Related: Interludial.
intermarriage (n.): 1570s, "act or fact of marrying" (now mostly restricted to legal use), from inter- + marriage. Meaning "marriage between members of different classes, tribes, etc." is from c. 1600.
intermarry (v.): 1570s, "to marry one another," from inter- + marry (v.). Meaning "to marry across families, castes, tribes, etc." is from 1610s. Related: Intermarried; intermarrying.
intermeddle (v.): late 14c., entremedlen, "to mix together, blend," from Anglo-French entremedler, Old French entremesler; from inter- + Anglo-French medler (see meddle (v.)). From early 15c. as "involve oneself in what is not one's business."
intermediacy (n.): 1713, from intermediate + -cy. Intermediateness is from 1826.
intermediary (adj.): 1757, "situated between two things;" 1818 as "serving as a mediator;" from French intermédiaire (17c.), from Latin intermedius "that which is between" (see intermediate). As a noun, "one who acts between others" from 1791 (Medieval Latin intermedium also was used as a noun). An earlier adjective was intermedial (1590s).
Intermediary, n., is, even with concrete sense of go-between or middleman or mediator, a word that should be viewed with suspicion & resorted to only when it is clear that every more ordinary word comes short of the need. [Fowler]
intermediate (adj.): "being or occurring between" (two things), early 15c., from Medieval Latin intermediatus "lying between," from Latin intermedius "that which is between," from inter- "between" (see inter-) + medius "in the middle" (see medial (adj.)).
intermediate (v.): c. 1600, "to interfere;" 1620s, "to mediate," from inter- "between" + mediate (v.). Related: Intermediated; intermediating.
intermediation (n.): c. 1600, noun of action from intermediate (v.).
interment (n.): early 14c., from Old French enterrement "burial, interment," from enterrer (see inter (v.)).
intermesh (v.): 1863, in reference to gears, from inter- "between" + mesh (v.). Related: Intermeshed; intermeshing.
intermezzo (n.): 1782, from Italian intermezzo "short dramatic performance (usually light and pleasing) between the acts of a play or opera," literally "that which is between," from Latin intermedius (see intermediate (adj.)).
intermigration (n.): "reciprocal migration," 1670s, from inter- "between" + migration.
interminable (adj.): late 14c., from Old French interminable (14c.) or directly from Late Latin interminabilis "endless," from in- "not" (see in- (1)) + terminabilis, from terminare "to limit, set bounds, end" (see terminus (adj.)). Related: Interminably.
interminate (adj.): 1530s, from Latin interminatus "unbounded, endless," from in- "not" (see in- (1)) + terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line" (see terminus).
intermingle (v.): late 15c. (trans.), from inter- "between" + mingle (v.). Intransitive sense from 1620s. Related: Intermingled; intermingling.
interministerial (adj.): 1917, in reference to branches of government, from inter- "between" + ministerial.
intermission (n.): early 15c., "fact of intermitting, temporary pause," from Latin intermissionem (nominative intermissio) "a breaking off, discontinuance, interruption," noun of action from past participle stem of intermittere "to leave off, leave an interval," from inter- "between" (see inter-) + mittere "let go, send" (see mission). Meaning "lapse of time between events" is from 1560s; specifically of performances (originally plays, later movies, etc.) from 1854.
Intermission is used in U.S. for what we call an interval (in a musical or dramatic performance). Under the influence of LOVE OF THE LONG WORD, it is beginning to infiltrate here and should be repelled; our own word does very well. [H.W. Fowler, "Modern English Usage," 1926]
intermissive (adj.): "not continuous," 1580s, from Latin intermiss-, past participle stem of intermittere "leave off, leave an interval" (see intermit).
intermit (v.): 1540s, "to interrupt" (obsolete); 1570s as "to discontinue for a time, suspend" (trans.) and "cease for a time" (intrans.), from Latin intermittere "to leave off, leave an interval, omit, suspend, interrupt, neglect," from inter- "between" (see inter-) + mittere "to send" (see mission). Related: Intermitted; intermitting.
intermittence (n.): 1796, from intermittent + -ence. Perhaps from French. Intermittency is from 1660s.
intermittent (adj.): c. 1600, from Latin intermittentem (nominative intermittens), present participle of intermittere "to leave off, cease, pause" (see intermission). Related: Intermittently.
intermitting (adj.): "stopping at intervals," 1620s, present-participle adjective from intermit (v.). Related: Intermittingly.
intermix (v.): 1550s (implied in intermixed), from inter- "between" + mix (v.). Originally transitive; intransitive sense is from 1722. Related: Intermixt; intermixing.
intermixture (n.): 1580s, "that which is mixed;" 1590s, "action of intermixing;" see inter- + mixture (n.).
intermodal (adj.): 1963, from inter- "between" + modal (adj.).
intermural (adj.): 1650s, from Latin intermuralis "situated between walls," from inter- "between" (see inter-) + murus (genitive muralis) "wall" (see mural).
intern (v.1): 1866, "to confine within set limits," from French interner "send to the interior, confine," from Middle French interne "inner, internal" (14c.), from Latin internus "within, internal" (see internal; also compare intern (n.)).