Words related to *leuk-
1590s, "bright, shining" (a sense now obsolete or restricted), from Latin lucidus "light, bright, clear," figuratively "perspicuous, lucid, clear," from lucere "to shine," from lux (genitive lucis) "light," from PIE root *leuk- "to shine, be bright."
Sense of "easy to understand, free from obscurity of meaning, marked by intellectual clarity" first recorded 1786. Lucid interval "period of calm or temporary sanity" (1580s) is from Medieval Latin lucida intervalla (plural), common in medieval legal documents (non est compos mentis, sed gaudet lucidis intervallis, etc.). The notion probably is of a period of calm and clear during a storm. Related: Lucidly; lucidness (1640s).
Old English Lucifer "Satan," also "morning star, Venus in the morning sky before sunrise," also an epithet or name of Diana, from Latin Lucifer "morning star," noun use of adjective, literally "light-bringing," from lux (genitive lucis) "light" (from PIE root *leuk- "light, brightness") + ferre "to carry, bear," from PIE root *bher- (1) "to carry," also "to bear children." Venus in the evening sky was Hesperus.
Belief that it was the proper name of Satan began with its use in Bible to translate Greek Phosphoros, which translates Hebrew Helel ben Shahar in Isaiah xiv.12 — "How art thou fallen from heaven, O Lucifer, son of the morning!" [KJV] Because of the mention of a fall from Heaven, the verse was interpreted spiritually by Christians as a reference to Satan, even though it is literally a reference to the King of Babylon (see Isaiah xiv.4). Sometimes rendered daystar in later translations.
As "friction match," 1831, short for Lucifer match (1831). Among the 16c. adjectival forms were Luciferian, Luciferine, Luciferous. There was a noted Bishop Lucifer of Cagliari in Sardinia in the 4th century, a strict anti-Arian regarded locally as a saint.
"shunning light" (in reference to bats, cockroaches, etc.), 1650s, from Latin lucifugus "light-shunning," from stem of lucere "to shine" (from suffixed (iterative) form of PIE root *leuk- "light, brightness") + stem of fugax "apt to flee, timid," figuratively "transitory, fleeting," from fugere "to flee" (see fugitive (adj.)).
1590s, "close study or thought;" 1610s, "a product of such study or thought, literary work showing signs of too-careful elaboration," from Latin lucubrationem (nominative lucubratio) "nocturnal study, night work," noun of action from past-participle stem of lucubrare, literally "to work by artificial light," from stem of lucere "to shine," from suffixed (iterative) form of PIE root *leuk- "light, brightness." Related: Lucubrations.
The current story in antiquity was that Aeschylus had been killed near Gela in Sicily by a tortoise dropt on his head by an eagle, which mistook the bald shiny pate of the venerable poet for a stone, and hoped to smash the tortoise on it. See Biographi Graeci, ed. Westermann, p. 120 ; Aelian Nat. Anim. vii. 16 ; Suidas, s.v. Αίσχύλοσ ; Valerius Maximus, ix. 12. Ext. 2. This important topic has produced the usual crop of learned dissertations. The late Professor F. G. Welcker gravely discussed it by the help of ornithological information derived from Aesop's fables, notes of travel made by the professor himself on the supposed scene of the catastrophe, and statistics as to the number of bald-headed men in antiquity. The interesting inquiry has since been prosecuted by other scholars with equal judgment and learning. The reader who desires to peruse these ponderous lucubrations should consult Rheinisches Museum, N.F. 7 (1850), pp. 139-144, 285 sq ; id., 9 (1854), pp. 148-155, 160* ; id., 37 (1882), pp. 308-312 ; Fleckeisen's Jahrbücher, 26 (1880), pp. 22-24 ; Welcker, Antike Denkmäler, 2. pp. 337-346. [J.G. Frazer, notes to Pausanias's "Description of Greece," 1898]