Etymology
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jealous (adj.)

c. 1200, gelus, later jelus, "possessive and suspicious," originally in the context of sexuality or romance (in any context from late 14c.), from Old French jalos/gelos "keen, zealous; avaricious; jealous" (12c., Modern French jaloux), from Late Latin zelosus, from zelus "zeal," from Greek zēlos, which sometimes meant "jealousy," but more often was used in a good sense ("emulation, rivalry, zeal"), from PIE root *ya- "to seek, request, desire" (see zeal). In biblical language (early 13c.) "tolerating no unfaithfulness." Also in Middle English sometimes in the more positive sense, "fond, amorous, ardent" (c. 1300) and in the senses that now go with zealous, which is a later borrowing of the same word, from Latin.

Most of the words for 'envy' ... had from the outset a hostile force, based on 'look at' (with malice), 'not love,' etc. Conversely, most of those which became distinctive terms for 'jealousy' were originally used also in a good sense, 'zeal, emulation.' [Buck, pp.1138-9]

Among the ways to express "jealous" in other tongues are Swedish svartsjuka, literally "black-sick," from phrase bara svarta strumpor "wear black stockings," also "be jealous." Danish skinsyg "jealous," literally "skin-sick," is from skind "hide, skin" said to be explained by Swedish dialectal expression fa skinn "receive a refusal in courtship."

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jealously (adv.)
late 14c., "in a zealous manner;" 1718, "in a suspicious and possessive manner," from jealous + -ly (2).
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jealousy (n.)
c. 1200 in reference to sexual possessiveness and suspicion, from Old French jalousie "enthusiasm, love, longing; jealousy" (12c.), from jalos "keen, zealous; avaricious; jealous" (see jealous). Also sometimes in Middle English in a sense "solicitude, carefulness, regard," the connecting notion being "watchfulness." Meaning "zeal, fervor, devotion" is from late 14c.
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zealous (adj.)
"full of zeal" (in the service of a person or cause), 1520s, from Medieval Latin zelosus "full of zeal" (source of Italian zeloso, Spanish celoso), from zelus (see zeal). The sense "fervent, inspired" was earlier in English in jealous (late 14c.), which is the same word but come up through French. Related: Zealously, zealousness.
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emulous (adj.)
"desirous of equaling or excelling," late 14c., from Latin aemulus "striving, rivaling," in a bad sense "envious, jealous," from aemulari "to rival" (see emulation). Related: Emulously.
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envious (adj.)
c. 1300, from Anglo-French envious, Old French envieus (13c.), earlier envidius "envious, jealous" (12c., Modern French envieux), from Latin invidiosus "full of envy" (source of Spanish envidioso, Italian invidioso, Portuguese invejoso), from invidia (see envy). Related: Enviously; enviousness.
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jujube (n.)
late 14c., "date-like fruit from a tree found in Asia," from Old French jujube or Medieval Latin jujuba (plural), ill-formed medieval representatives of Late Latin zizyphum, from zizyphus, name of an Asiatic tree with datelike fruit, from Greek zizyphon, from Persian zayzafun. For consonant shift, compare jealous from zealous. The meaning "soft candy with date-like flavor" first recorded 1835.
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Juno 
Roman goddess of adult women and marriage, sister and wife of Jupiter, mid-14c., probably literally "the young one" (if so, perhaps as goddess of the new moon), from Proto-Italic *juwen- "young," which also is the source of Latin iunior "younger," iuvenis "young man" (see young (adj.)). Noted for her stately beauty and fits of jealous rage. Also the patron of national finances. Usually identified with Greek Hera, but Juno also had qualities of Athena.
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impulsive (adj.)

early 15c., originally in reference to medicine that reduces swelling or humors, from Medieval Latin impulsivus, from Latin impuls-, past participle stem of impellere "strike against, push against" (see impel). Meaning "having the property of impelling" (of force, cause, energy, etc.) is from c. 1600. Of persons, "rash, characterized by impulses," from 1847, from impulse. Earlier, at least once, in reference to maniacs:

The impulsive insane are often irritable, restless and jealous. Sometimes they have delusions, and sometimes not. Their delusions frequently seem to have no connection with their outbreaks of violence. They are often the best and at the same time the most dangerous class of patients in the asylums. They have little of the charity of the world, are most likely to be punished for their offences, and yet have the least control over their conduct. ["Impulsive and Homicidal Insanity," Boston Medical and Surgical Journal, April 19, 1843]
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egomania (n.)

"obsessive self-centeredness," 1825 (in a letter of English critic William Sidney Walker, published in 1852), from ego + mania. Not in common use before 1890s, where it translated German Ich-Sucht.

[The egomaniac, as opposed to the megalomaniac,] does not regard it as necessary to dream of himself as occupying some invented social position. He does not require the world or its appreciation to justify in his own eyes himself as the sole object of his own interest. He does not see the world at all. Other people simply do not exist for him. The whole 'non-Ego' appears in his consciousness merely as a vague shadow or a thin cloud. The idea does not even occur to him that he is something out of the common, that he is superior to other people, and for this reason either admired or hated ; he is alone in the world ; more than that, he alone is the world and everything else, men, animals, things are unimportant accessories, not worth thinking about. [Max Nordau, "Degeneration," English translation, 1895]

Nordau's book was much-read, debated, and cited at the time and the word was associated with him (e.g. The Agora, July 1895).

Walker's use aside, its infrequent print appearance before 1895 seems to have been largely in the side of medicine that dealt with psychological matters:

The most frequent, yet the most extraordinary of these perversions of temper, are seen in young females. It is a species of aberration of the intellect, but short of insanity, real enough, but exaggerated, fictitious, factitious, and real at the same time. It frequently has its origin in dyspepsia, hysteria, or other malady, and in emotion of various kinds, such as disappointment, vexation, &c. Its object is frequently to excite and to maintain a state of active sympathy and attention, for which there, is as it were, a perpetual, morbid, and jealous thirst. It was rather aptly designated, by the clever relative of one patient, an ego-mania. [Marshall Hall, M.D., "Practical Observations and Suggestions in Medicine," London, 1845]
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