"opposition to the advancement and diffusion of knowledge, a desire to prevent inquiry or enlightenment," 1801, from German obscurantism, obscurantismus (by 1798); see obscurant + -ism.

"one who opposes the progress of intellectual enlightenment," 1827; see obscurantism + -ist. As an adjective by 1841.

1540s, "act of darkening; state of being made dark," from Latin obscurationem (nominative obscuratio) "a darkening, obscuring," noun of action from past-participle stem of obscurare "to make dark, darken, obscure," from obscurus (see obscure (adj.)). 

c. 1400, "dark," figuratively "morally unenlightened; gloomy," from Old French obscur, oscur "dark, clouded, gloomy; dim, not clear" (12c.) and directly from Latin obscurus "dark, dusky, shady," figuratively "unknown; unintelligible; hard to discern; from insignificant ancestors," from ob "over" (see ob-) + -scurus "covered," from PIE root *(s)keu- "to cover, conceal." Related: Obscurely.

The figurative sense of "not readily understood, not manifest to the mind or understanding" is from early 15c.; of persons, "not illustrious or noted, unknown to fame," 1540s. The more literal sense of "indistinct, without clearness of form or outline, hardly perceptible, not capable of being clearly seen through lack of light" is attested in English from 1590s.

In regard to the meaning of something said or written, obscure is general, being founded upon the figure of light which is insufficient to enable one to see with any clearness; this figure is still felt in all the uses of the word. [Century Dictionary, 1895]

early 15c., obscuren, "to cover (something), cloud over," from obscure (adj.) or else from Old French obscurer, from Latin obscurare "to make dark, darken, obscure," from obscurus. Meaning "to conceal from knowledge or observation, disguise" is from 1520s; that of "to overshadow or outshine" is from 1540s. Related: Obscured; obscuring.

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]

late 14c., obsecracioun, "prayer, earnest entreaty," especially "a prayer of supplication," from Latin obsecrationem (nominative obsecratio) "a beseeching, imploring, supplication, entreaty," noun of action from past-participle stem of obsecrare "to beseech, entreat" (on religious grounds), from ob "in front of, before" (see ob-) + sacrare "to make or declare sacred" (see sacred).

late 15c., "prompt to serve, meekly compliant with the will or wishes of another, dutiful," from Latin obsequiosus "compliant, obedient," from obsequium "compliance, dutiful service," from obsequi "to accommodate oneself to the will of another," from ob "after" (see ob-) + sequi "to follow" (from PIE root *sekw- (1) "to follow"). Pejorative sense of "fawning, sycophantic, unduly compliant" had emerged by 1590s. Related: Obsequiously; obsequiousness (mid-15c.).

late 14c., obsequi, in plural, "funeral rites, a funeral," from Anglo-French obsequie, Old French obseque, osseque "funeral rites" and directly from Medieval Latin obsequiae, influenced in sense by confusion of Latin obsequium "compliance" (see obsequious) with exsequiae "funeral rites." Typically in plural, obsequies.