"effort to equal or excel in qualities or actions that one admires in another or others; imitative rivalry," 1550s, from French émulation (13c.) and directly from Latin aemulationem (nominative aemulatio) "rivalry, emulation, competition," noun of action from past-participle stem of aemulari "to rival, strive to excel," from aemulus "striving, rivaling" (also as a noun, "a rival," fem. aemula), from Proto-Italic *aimo-, from PIE *aim-olo, suffixed form of root *aim- "copy" (from PIE root *aim- "to copy").
"to strive to equal or excel in qualities or actions," 1580s, a back-formation from emulation, or else from Latin aemulatus, past participle of aemulari "to rival." Related: Emulated; emulating; emulable; emulative.
Proto-Indo-European root meaning "to copy."
It is the hypothetical source of/evidence for its existence is provided by: Latin imago "image," aemulus "emulous," imitari "to copy, portray, imitate;" Hittite himma- "imitation, substitute."
"passionate ardor in pursuit of an objective or course of action," late 14c., from Old French zel (Modern French zèle) and directly from Late Latin zelus "zeal, emulation" (source also of Italian zelo, Spanish celo), a Church word, from Greek zēlos "ardor, eager rivalry, emulation," "a noble passion" [Liddell & Scott], but also "jealousy;" from PIE *ya- "to seek, request, desire." From mid-15c. as "devotion."
c. 1400, "emulation; act of copying," from Old French imitacion, from Latin imitationem (nominative imitatio) "a copying, imitation," noun of action from past participle stem of imitari "to copy, portray, imitate," from PIE *im-eto-, from root *aim- "to copy." Meaning "an artificial likeness" is from c. 1600. As an adjective, from 1840.
Scandinavian masc. proper name, popular with early kings, the first to use it was Magnus I, king of Norway and Denmark (d. 1047), who evidently took it in emulation of Charlemagne (Latin Carolus Magnus) under the impression that magnus (Latin, literally "great," from PIE root *meg- "great") was a personal name.
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."