unfading (adj.)

prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").

The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.

It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.

early 14c., "lose brightness, grow pale," from Old French fader "become weak, wilt, wither," from fade (adj.) "pale, weak; insipid, tasteless" (12c.), probably from Vulgar Latin *fatidus, which is said to be a blending of Latin fatuus "silly, tasteless" and vapidus "flat, flavorless." Related: Faded; fading. Of sounds, by 1819. Transitive sense from 1590s; in cinematography from 1918.

Adieu! adieu! thy plaintive anthem fades

  Past the near meadows, over the still stream,

    Up the hill-side; and now 'tis buried deep

      In the next valley-glades:

Was it a vision, or a waking dream?

  Fled is that music:" Do I wake or sleep?

[Keats, from "Ode to a Nightingale"]