light (n.) Look up light at Dictionary.com
"brightness, radiant energy," Old English leht, earlier leoht "light, daylight," from Proto-Germanic *leukhtam (source also of Old Saxon lioht, Old Frisian liacht, Middle Dutch lucht, Dutch licht, Old High German lioht, German Licht, Gothic liuhaþ "light"), from PIE *leuk- "light, brightness" (source also of Sanskrit rocate "shines;" Armenian lois "light," lusin "moon;" Greek leukos "bright, shining, white;" Latin lucere "to shine," lux "light," lucidus "clear;" Old Church Slavonic luci "light;" Lithuanian laukas "pale;" Welsh llug "gleam, glimmer;" Old Irish loche "lightning," luchair "brightness;" Hittite lukezi "is bright").

The -gh- was an Anglo-French scribal attempt to render the Germanic hard -h- sound, which has since disappeared from this word. The figurative spiritual sense was in Old English; the sense of "mental illumination" is first recorded mid-15c. Meaning "something used for igniting" is from 1680s. Meaning "a consideration which puts something in a certain view (as in in light of) is from 1680s. Something that's a joy and a delight has been the light of (someone's) eyes since Old English:
Ðu eart dohtor min, minra eagna leoht [Juliana].
To see the light "come into the world" is from 1680s; later in a Christian sense.
light (v.1) Look up light at Dictionary.com
"touch down," from Old English lihtan "to alight; alleviate, leave," from Proto-Germanic *linkhtijan, literally "to make light," from *lingkhtaz "not heavy" (see light (adj.1)). Apparently the ground sense is "to dismount a horse, etc., and thus relieve it of one's weight." To light out "leave hastily" is 1870, from a nautical meaning "move out, move heavy objects," of unknown origin but perhaps belonging to this word (compare lighter (n.1)).
light (v.2) Look up light at Dictionary.com
"to shed light; to set on fire," late Old English lihtan (Anglian), liehtan (West Saxon), originally transitive, "to ingite, set on fire," also in a spiritual sense, "to illuminate, fill with brightness." It is common Germanic (cognates: Old Saxon liohtian, Old High German liuhtan, German leuchten, Gothic liuhtjan "to light"), from the source of light (n.).

Meaning "to shed light, illuminate," also "to furnish light for" are from c. 1200; sense of "emit light, shine" is from c. 1300. Buck writes that light is "much more common than kindle even with fire, and only light, not kindle, with candle, lamp, pipe, etc." Related: Lighted; lighting.
light (adj.2) Look up light at Dictionary.com
"not dark," Old English leoht, common Germanic (cognates: Old Saxon and Old High German lioht, Old Frisian liacht, German licht "bright," from the source of Old English leoht (see light (n.)). Meaning "pale-hued" is from 1540s.
light (adj.1) Look up light at Dictionary.com
"not heavy," from Old English leoht "not heavy, light in weight; easy, trifling; quick, agile," from Proto-Germanic *lingkhtaz (source also of Old Norse lettr, Swedish lätt, Old Frisian, Middle Dutch licht, German leicht, Gothic leihts), from PIE root *legwh- "not heavy, having little weight" (source also of Latin levis "light," Old Irish lu "small;" see lever).

The notion in make light of (1520s) is "unimportance." Alternative spelling lite, the darling of advertisers, is first recorded 1962. The adverb is Old English leohte, from the adjective. Light-skirts "woman of easy virtue" is attested from 1590s.