"state or character of shining brightly; a flood of light," 1630s, from Latin refulgentia "reflected luster, splendor," from refulgens, present participle of refulgere "flash back, shine brilliantly," from re- "back" (see re-) + fulgere "to shine" (from PIE *bhleg- "to shine, flash," from root *bhel- (1) "to shine, flash, burn"). Related: Refulgency (1610s).
1836, from French margarine, a chemical term given to a fatty substance obtained from animal and vegetable oil, coined by French chemist Michel Eugène Chevreul (1786-1889) in 1813 from (acide) margarique "margaric (acid);" literally "pearly," from Greek margaritēs "pearl" (see Margaret). So called for the luster of the crystals. Now discarded in this sense as a chemical term, but preserved in margarine.
Figurative sense of "distinguished by admirable qualities" is from 1848. Of diamonds from 1680s in reference to a flat-topped cut invented 17c. by Venetian cutter Vincenzo Peruzzi. Related: Brilliantly; brilliantness.
mid-15c. ternishen, "become tarnished; discolor," from Old French terniss-, present-participle stem of ternir "dull the luster or brightness of, make dim" (15c.), probably from terne (adj.) "dull, dark," which according to Diez is from a Germanic source cognate with Old High German tarnjan "to conceal, hide," Old English dyrnan "to hide, darken," from Proto-Germanic *darnjaz (see dern), but there are difficulties of form, sense, and date. Figurative sense is from 1690s. Related: Tarnished; tarnishing.
The other verb, meaning "to add luster, make smooth and shining," is from 1650s, from gloss (n.1). Figurative sense of "smooth over, hide" is from 1729, mostly from the first verb, in its extended sense of "explain away, veil or shift the meaning of," but showing influence of the second. Related: Glossed; glossing.
c. 1200, ournement, "an accessory; something that serves primarily for use but also may serve as adornment; ornamental apparel, jewels," from Old French ornement "ornament, decoration," and directly from Latin ornamentum "apparatus, equipment, trappings; embellishment, decoration, trinket," from ornare "to equip, adorn," from stem of ordo "row, rank, series, arrangement" (see order (n.)).
The sense shift in English to "something employed simply to adorn or decorate, something added as an embellishment, whatever lends grace or beauty to that to which it is added or belongs" is by late 14c. (this also was a secondary sense in classical Latin). Meaning "outward appearance, mere display" is from 1590s. The figurative use is from 1550s; the meaning "one who adds luster to one's sphere or surroundings" is from 1570s.
late 15c., obscurite, "absence of light, lack of brightness or luster;" 1610s with the meaning "condition of being unknown or inconspicuous;" from obscure (adj.) + -ity; or else from Old French obscurete, a variant of oscureté "darkness, gloom; vagueness, confusion; insignificance" (14c.) and directly from Latin obscuritatem (nominative obscuritas) "darkness, indistinctness, uncertainty," from obscurus. Meaning "quality or condition of not being clearly comprehended" is from late 15c. (Caxton).
When I was asked to talk about the Obscurity of the Modern Poet I was delighted, for I have suffered from this obscurity all my life. But then I realized that I was being asked to talk not about the fact that people don't read poetry, but about the fact that most of them wouldn't understand it if they did .... [Randall Jarrell, "The Obscurity of Poetry," 1953]