mirage 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.

mid-12c., "a wondrous work of God," from Old French miracle (11c.) "miracle, story of a miracle, miracle play," from Latin miraculum "object of wonder" (in Church Latin, "marvelous event caused by God"), from mirari "to wonder at, marvel, be astonished," figuratively "to regard, esteem," from mirus "wonderful, astonishing, amazing," earlier *smeiros, from PIE *smei- "to smile, laugh" (source also of Sanskrit smerah "smiling," Greek meidan "to smile," Old Church Slavonic smejo "to laugh;" see smile (v.)). The Latin word is the source of Spanish milagro, Italian miracolo. 

From mid-13c. as "something that excites wonder or astonishment, extraordinary or remarkable feat," without regard to divinity or supernatural power. It replaced Old English wundortacen, wundorweorc. The Greek words rendered as miracle in the English bibles were semeion "sign," teras "wonder," and dynamis "power," which in the Vulgate were translated respectively as signum, prodigium, and virtus.

Miracle-drug is by 1939 (in reference to sulfanilamide). Miracle-worker "a thaumaturge" is from 1560s (Middle English had mircleour, early 15c.). Miracle-play "medieval dramatic representation of the life of Christ or a saint or other sacred subjects" is by 1744 (miraclis pleynge is from c. 1400). The condiment Miracle Whip was introduced 1933 by Kraft Foods; apparently the name was first given to the patented machine that made it.