Etymology
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knowledge (n.)

early 12c., cnawlece "acknowledgment of a superior, honor, worship;" for the first element see know (v.). The second element is obscure, perhaps from Scandinavian and cognate with the -lock "action, process," found in wedlock.

From late 14c. as "capacity for knowing, understanding; familiarity;" also "fact or condition of knowing, awareness of a fact;" also "news, notice, information; learning; organized body of facts or teachings." The sense of "sexual intercourse" is from c. 1400. Middle English also had a verb form, knoulechen "acknowledge" (c. 1200), later "find out about; recognize," and "to have sexual intercourse with" (c. 1300); compare acknowledge.

Since Knowledge is but sorrow's Spy,
   It is not safe to know.
[Davenant, song from "The Just Italian," 1630]


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knowledgeable (adj.)

also knowledgable, c. 1600, "capable of being known, recognizable" (a 17c. sense now obsolete), from knowledge in its Middle English verbal sense + -able. The sense of "having knowledge, displaying mental capacity" is from 1829 and probably a new formation.

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foreknowledge (n.)

"prescience," 1530s, from fore- + knowledge. Earlier in this sense was foreknowing (late 14c.), from foreknow "have previous knowledge of, know beforehand." Old English had forewitan, Middle English forwiten "to foreknow."

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acknowledge (v.)

late 15c., "admit or show one's knowledge," a blend of Middle English aknow "admit or show one's knowledge" and Middle English knowlechen "admit, acknowledge" (c. 1200; see knowledge). Middle English aknow is from Old English oncnawan "understand, come to recognize," from on (see on (prep.)) + cnawan "recognize;" see know).

"By 16th c. the earlier vbs. knowledge and a(c)know ... were obs., and acknowledge took their place" [OED]. In the merger, an unetymological -c- slipped in; perhaps the explanation is that when English kn- became a simple "n" sound, the -c- stepped up to preserve, in this word, the ancient "kn-" sound. Related: Acknowledged; acknowledging.

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*gno- 

*gnō-, Proto-Indo-European root meaning "to know."

It forms all or part of: acknowledge; acquaint; agnostic; anagnorisis; astrognosy; can (v.1) "have power to, be able;" cognition; cognizance; con (n.2) "study;" connoisseur; could; couth; cunning; diagnosis; ennoble; gnome; (n.2) "short, pithy statement of general truth;" gnomic; gnomon; gnosis; gnostic; Gnostic; ignoble; ignorant; ignore; incognito; ken (n.1) "cognizance, intellectual view;" kenning; kith; know; knowledge; narrate; narration; nobility; noble; notice; notify; notion; notorious; physiognomy; prognosis; quaint; recognize; reconnaissance; reconnoiter; uncouth; Zend.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jna- "know;" Avestan zainti- "knowledge," Old Persian xšnasatiy "he shall know;" Old Church Slavonic znati "recognizes," Russian znat "to know;" Latin gnoscere "get to know," nobilis "known, famous, noble;" Greek gignōskein "to know," gnōtos "known," gnōsis "knowledge, inquiry;" Old Irish gnath "known;" German kennen "to know," Gothic kannjan "to make known."

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epistemic (adj.)

"pertaining to knowledge," 1886, from Greek episteme "knowledge," especially scientific knowledge (see epistemology) + -ic.

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omniscient (adj.)

"possessing knowledge of all things, having universal knowledge," c. 1600, from Modern Latin omniscientem (nominative omnisciens) "all-knowing," a back-formation from Medieval Latin omniscientia "all-knowledge," from Latin omnis "all" (see omni-) + scientia "knowledge" (see science). Related: Omnisciently.

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sciolism (n.)

"a show of knowledge, unfounded pretense to profound knowledge," 1798; see sciolist + -ism.

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omniscience (n.)

"infinite knowledge, the quality or attribute of fully knowing all things," 1610s, from Medieval Latin omniscientia "all-knowledge," from Latin omnis "all" (see omni-) + scientia "knowledge" (see science).

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gnosis (n.)

"knowledge," especially "special knowledge of spiritual mysteries," 1703, from Greek gnōsis "a knowing, knowledge; a judicial inquiry, investigation; a being known," in Christian writers, "higher knowledge of spiritual things," from PIE *gnō-ti-, from root *gno- "to know."

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