Etymology
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episode (n.)

1670s, "commentary between two choric songs in a Greek tragedy," also "an incidental narrative or digression within a story, poem, etc.," from French épisode or directly from Greek epeisodion "an episode," literally "an addition," noun use of neuter of epeisodios "coming in besides," from epi "in addition" (see epi-) + eisodos "a coming in, entrance" (from PIE root *en "in").

The second element is a compound of eis "into" + hodos "a way, path; a journey; a method, system," a word of uncertain origin (see Exodus). Transferred sense of "outstanding incident, experience" first recorded in English 1773. Transferred by 1930s to individual broadcasts of serial radio programs.

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episodic (adj.)
1711, from episode + -ic. Episodical is from 1660s.
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*en 
Proto-Indo-European root meaning "in."

It forms all or part of: and; atoll; dysentery; embargo; embarrass; embryo; empire; employ; en- (1) "in; into;" en- (2) "near, at, in, on, within;" enclave; endo-; enema; engine; enoptomancy; enter; enteric; enteritis; entero-; entice; ento-; entrails; envoy; envy; episode; esoteric; imbroglio; immolate; immure; impede; impend; impetus; important; impostor; impresario; impromptu; in; in- (2) "into, in, on, upon;" inchoate; incite; increase; inculcate; incumbent; industry; indigence; inflict; ingenuous; ingest; inly; inmost; inn; innate; inner; innuendo; inoculate; insignia; instant; intaglio; inter-; interim; interior; intern; internal; intestine; intimate (adj.) "closely acquainted, very familiar;" intra-; intricate; intrinsic; intro-; introduce; introduction; introit; introspect; invert; mesentery.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit antara- "interior;" Greek en "in," eis "into," endon "within;" Latin in "in, into," intro "inward," intra "inside, within;" Old Irish in, Welsh yn, Old Church Slavonic on-, Old English in "in, into," inne "within, inside."
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cliff-hanger (n.)

also cliffhanger, "suspenseful situation," 1950, a transferred use from an earlier meaning "movie serial" (1937), from cliff + hang (v.). In some U.S. continued-next-week silent cinema serials in the "Perils of Pauline" days, the episode often ended with the heroine "hanging over a cliff from a fraying rope through which the villain was sawing with a dull knife, to be saved by Crane Wilbur or Milton Sills" [Collier's magazine, July 6, 1946].

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monsoon (n.)

1580s, "alternating trade wind of the Indian Ocean," from Dutch monssoen, from Portuguese monçao, from Arabic mawsim "time of year, appropriate season" (for a voyage, pilgrimage, etc.), from wasama "he marked." The Arabic word, picked up by Portuguese sailors in the Indian Ocean, was used for anything that comes round every year (such as a festival), and was extended to the season of the year when the monsoon blows from the southwest (April through October) and the winds were right for voyages to the East Indies. In India, the summer monsoon is much stronger than the winter and was popularly spoken of emphatically as "the monsoon." It also brings heavy rain, hence the meaning "heavy episode of rainfall during the rainy season" (1747). Related: Monsoonal.

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affair (n.)

c. 1300, "what one has to do, ordinary business," from Anglo-French afere, Old French afaire "business, event; rank, estate" (12c., Modern French affaire), from the infinitive phrase à faire "to do," from Latin ad "to" (see ad-) + facere "to do, make" (from PIE root *dhe- "to set, put").

According to OED a Northern word originally, brought into general use and given a French spelling by Caxton (15c.). General sense of "vague proceedings" (in romance, war, etc.) first attested 1702. Meaning "an affair of the heart; a passionate episode" is from French affaire de coeur (itself attested as a French phrase in English from 1809); to have an affair with someone in this sense is by 1726, earlier have an affair of love:

'Tis manifeſtly contrary to the Law of Nature, that one Woman ſhould cohabit or have an Affair of Love with more than one Man at the ſame time. ["Pufendorf's Law of Nature and Nations," transl. J. Spavan, London, 1716]

Related: Affairs.

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pilot (n.)

1510s, "one who steers a ship," especially one who has charge of the helm when the ship is passing in or out of harbor, from French pillote (16c.), from Italian piloto, supposed to be an alteration of Old Italian pedoto, which usually is said to be from Medieval Greek *pedotes "rudder, helmsman," from Greek pedon "steering oar," related to pous (genitive podos) "foot," from PIE root *ped- "foot." The change of -d- to -l- in Latin-derived languages ("Sabine -l-") parallels that in odor/olfactory; see lachrymose.

The transferred or figurative sense "a guide, a director of the course of others" is by 1590s. The literal sense was extended by 1848 to "one who controls a balloon," and by 1907 to "one who flies an airplane."

As an adjective, 1788 as "pertaining to a pilot;" from 1928 as "serving as a prototype," thus the noun pilot meaning "pilot episode" (etc.), attested from 1962. A pilot light (by 1890) is a very small light kept burning beside a large burner to automatically light the main burner when the flow is turned on.

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period (n.)

early 15c., periode, "a course or extent of time; a cycle of recurrence of a disease," from Old French periode (14c.) and directly from Medieval Latin periodus "recurring portion, cycle," from Latin periodus "a complete sentence," also "cycle of the Greek games," from Greek periodos "cycle, circuit, period of time," literally "a going around," from peri "around" (see peri-) + hodos "a going, traveling, journey; a way, path, road," a word of uncertain origin (see Exodus).

Sense of "repeated cycle of events" led to that of "interval of time." From 1712 as "an indefinite part of any continued state or series of events;" by 1727 as "time in which a circuit or revolution (as of a heavenly body) is made." Sense of "episode of menstruation" is by 1829, probably short for period of menstruation (1808), etc.  

The meaning "dot marking end of a sentence" is recorded c. 1600, from the earlier sense of "a complete sentence, from one full stop to another," then "a full pause at the end of a sentence" (1580s). The educational sense of "portion of time set apart for a lesson" is from 1876. The sporting sense "division of a game or contest" is attested by 1898. As an adjective from 1905; period piece is attested from 1911.

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