"measurement of the range of vision; measurement of the visual powers in general," 1886, from optometer (1738), name given to an instrument for testing vision, from opto- "sight," from Greek optos "seen, visible" (from PIE root *okw- "to see") + -metry "a measuring of." Probably influenced by French optométrie.
When I made the foregoing Experiments, I designed to repeat them with more Care and Exactness, and to make some new ones of the same Sort, by means of an Instrument I had contrived for that Purpose; which from its Use in measuring the Limits of distinct Vision, and in determining with great Exactness the Strength and Weakness of Sight, may be called an Optometer. [Dr. William Porterfield, "An Essay Concerning the Motions of our Eyes, Part II," in Medical Essays and Observations, Vol. IV, Edinburgh, 1738]
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"]