1660s, "action of enlightening," from enlighten + -ment. Used only in figurative sense, of spiritual enlightenment, etc. Attested from 1865 as a translation of German Aufklärung, a name for the spirit of independent thought and rationalistic system of 18c. Continental philosophers.

For the philosophes, man was not a sinner, at least not by nature; human nature — and this argument was subversive, in fact revolutionary, in their day — is by origin good, or at least neutral. Despite the undeniable power of man's antisocial passions, therefore, the individual may hope for improvement through his own efforts — through education, participation in politics, activity in behalf of reform, but not through prayer. [Peter Gay, "The Enlightenment"]

"the Enlightenment," 1801, from German Aufklärung (18c.), literally "enlightenment," from aufklären "to enlighten" (17c.), from auf "up" (from PIE root *upo "under," also "up from under") + klären "to clear," from Latin clarus (see clear (adj.)).

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

in Zen Buddhism, "enlightenment," 1727, from Japanese, said to mean literally "spiritual awakening."

late 14c., "spiritual enlightenment," from Late Latin illuminationem (nominative illuminatio), noun of action from past participle stem of Latin illuminare "to throw into light, make bright, light up;" figuratively, in rhetoric, "to set off, illustrate," from assimilated form of in- "in, into" (from PIE root *en "in") + lumen (genitive luminis) "light," from suffixed form of PIE root *leuk- "light, brightness." Meaning "action of lighting" in English is from 1560s; sense of "intellectual enlightenment" is from 1630s.

"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.

also philosoph, "Enlightenment rationalist and skeptic," especially in reference to any of the French Encyclopædists, often disparaging or with contemptuous implication (when used by believers), 1774, from French philosophe, literally "philosopher" (Old French filosofe; see philosopher). Usually italicized in English, but nativized by Peter Gay ("The Enlightenment," 1966) and others. Also compare philosophist. It also was the older word for "philosopher" in English, from Old English to c. 1400.

1680s, from Sinhalese bo, from Pali bodhi, short for bodhi-taru "bo tree," literally "tree of wisdom or enlightenment" (related to Sanskrit buddhah "awakened," from PIE root *bheudh- "be aware, make aware") + taru "tree."

"that obscures or darkens; that labors to prevent enlightenment," 1804, from French obscurant, from Latin obscurantem (nominative obscurans), present participle of obscurare "to make dark, darken, obscure," from obscurus (see obscure (adj.)).

late 15c., "business of being a priest, exercise of priestly functions," from priest + craft (n.). After rise of Protestantism and the Enlightenment, it acquired a pejorative sense of "arts and devices of ambitious priests for attaining and holding temporal power and social control" (1680s).