Etymology
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mirror (n.)

mid-13c., mirour, "polished surface (of metal, coated glass, etc.) used to reflect images of objects," especially the face of a person, from Old French mireoir "a reflecting glass, looking glass; observation, model, example," earlier miradoir (11c.), from mirer "look at" (oneself in a mirror), "observe, watch, contemplate," from Vulgar Latin *mirare "to look at," variant of Latin mirari "to wonder at, admire" (see miracle).

The Spanish cognate, mirador (from mirar "to look, look at, behold"), has come to mean "watch tower, gallery commanding an extensive view." Latin speculum "mirror" (or its Medieval Latin variant speglum) is the source of words for "mirror" in neighboring languages: Italian specchio, Spanish espejo, Old High German spiegal, German Spiegel, Dutch spiegel, Danish spejl, Swedish spegel. An ancient Germanic group of words for "mirror" is represented by Gothic skuggwa, Old Norse skuggsja, Old High German scucar, which are related to Old English scua "shade, shadow."

Words for 'mirror' are mostly from verbs for 'look', with a few words for 'shadow' or other sources. The common use of the word for the material 'glass' in the sense of 'mirror' seems to be peculiar to English. [Carl Darling Buck, "A Dictionary of Selected Synonyms in the Principal Indo-European Languages," 1949]

Figurative use, "that in or by which anything is shown or exemplified," hence "a model (of good or virtuous conduct)" is attested from c. 1300. Mirrors have been used in divination since classical and biblical times, and according to folklorists, in modern England they are the subject of at least 14 known superstitions. Belief that breaking one brings bad luck is attested from 1777. Mirror image "something identical to another but having right and left reversed" is by 1864. Mirror ball attested from 1968. To look in (the) mirror in the figurative sense of "examine oneself" is by early 15c.

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mirror (v.)
"to reflect," 1590s, from mirror (n.). Related: Mirrored; mirroring. The Middle English verb mirouren (early 15c.) meant "to be a model" (for conduct, behavior, etc.), while miren (mid-14c., from Old French mirer) meant "to look in a mirror."
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mirage (n.)

"optical illusion of objects reflected in a sheet of water in hot, sandy deserts," 1800, in translations of French works, from French mirage (1753), from se mirer "to be reflected," from Latin mirare (see mirror (n.)). Or the French word is from Latin mirus "wonderful" (see miracle). The similarity to Arabic mi'raj has been noted, but the usual sense of that word is "ladder, stairs; climb, ascent," and the resemblance appears to be coincidental. The standard Arabic for "a desert mirage" is sarāb. The figurative sense of "deceptiveness of appearance, a delusive seeming" is by 1812. The phenomenon is produced by excessive bending of light rays through layers of air of different densities, producing distorted, displaced, or inverted images.

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catoptromancy (n.)
"divination by means of a mirror," 1610s, from Latinized combining form of Greek katoptron "mirror" (see catoptric) + -mancy "divination by means of."
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specular (adj.)
1570s, "reflective" (like a mirror), from Latin specularis, from speculum "a mirror" (see speculum). Meaning "assisting in vision; affording a view" is from 1650s, from Latin speculari "to spy" (see speculation).
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catoptric (adj.)
"pertaining to mirrors or a mirror," 1774, from Latinized form of Greek katoptrikos, from katoptron "mirror," from kata "against" (see cata-) + stem of optos "seen, visible" (from PIE root *okw- "to see") + instrumental suffix -tron. Related: Catoptrics; catoptrical.
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shower (n.2)
"one who shows," Old English sceawere "spectator, watchtower, mirror," agent noun; see show (v.).
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skyjack (v.)
"to hijack an airplane," 1961, apparently coined in New York "Mirror" headlines, from sky (n.) + second element of hijack (q.v.).
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enoptomancy (n.)
divination by means of a mirror, 1855, from Greek enoptos, literally "seen in," from en- "in" (from PIE root *en "in") + optos "seen, visible" (from PIE root *okw- "to see") + -mancy.
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speculum (n.)
1590s, in surgery and medicine, "instrument for rendering a part accessible to observation," from Latin speculum "reflector, looking-glass, mirror" (also "a copy, an imitation"), from specere "to look at, view" (from PIE root *spek- "to observe"). As a type of telescope attachment from 1704.
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