Etymology
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adjure (v.)

late 14c., adjuren, "to bind by oath; to question under oath;" c. 1400 as "to charge with an oath or under penalty of a curse," from Latin adiurare "confirm by oath, add an oath, to swear to in addition; call to witness," in Late Latin "to put (someone) to an oath," from ad "to" (see ad-) + iurare "swear," from ius (genitive iuris) "law" (see jurist). Related: Adjured; adjuring.

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perjury (n.)

late 14c., perjurie, in law, "the act of swearing to a statement known to be false, willful utterance of false testimony under oath," via Anglo-French perjurie (late 13c.) and Old French parjure "perjury, false witness," both from Latin periurium "a false oath," from periurare "swear falsely," from per "away, entirely" (see per) + iurare "to swear" (see jury (n.)). Related: Perjurious.

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hearsay (n.)
"information communicated by another, gossip," mid-15c., from phrase to hear say (Middle English heren seien, Old English herdon secgan). The notion is "hear (some people) say;" from hear (v.) + say (v.). As an adjective from 1570s. Hearsay evidence (1670s) is that which the witness gives not from his own perception but what was told to him. Compare similar formation in Dutch hooren zeggen, German hörensagen.
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seer (n.)

late 14c., "one to whom divine revelations are made, prophet, person who sees or foretells future events," agent noun from see (v.). Originally rendering Latin videns, Greek bleptor (rendering Hebrew roeh) in Bible translations (such as I Kings ix.9). The rare literal sense of "one who sees or can see, a beholder, witness, watcher" is attested from early 15c.

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certify (v.)

mid-14c., "to declare the truth of," also "to vouch for or confirm" (an official record, etc.), from Old French certefiier "make certain, witness the truth of" (12c.), from Late Latin certificare "to certify, to make certain," from Latin certus "fixed, sure" (see certain) + root of facere "to make, do" (from PIE root *dhe- "to set, put"). Also used in Middle English in broader senses of "inform, give notice to; instruct, to direct; to designate." Related: Certified; certifying.

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suborn (v.)

"to procure unlawfully, to bribe to accomplish a wicked purpose," especially to induce a witness to perjury, "to lure (someone) to commit a crime," 1530s, from French suborner "seduce, instigate, bribe" (13c.) and directly from Latin subornare "employ as a secret agent, incite secretly," originally "equip, fit out, furnish," from sub "under; secretly" (see sub-) + ornare "equip," related to ordo "row, rank, series, arrangement" (see order (n.)). Related: Suborned; suborning.

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protest (v.)

mid-15c., protesten, "to declare or state formally or solemnly, bear witness or testimony to," from Old French protester and directly from Latin protestari "declare publicly, testify, protest" (see protest (n.)). Original sense preserved in to protest one's innocence. The meaning "make a solemn or formal declaration (often in writing) in condemnation of an act or measure, proposed or accomplished," is from c. 1600. The word's association with marches and rallies arose in 20c. Related: Protested; protesting.

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liar (n.)
"one who knowingly utters falsehoods," early 13c., from Old English leogere "liar, false witness, hypocrite," agent noun from Anglian legan, West Saxon leogan "be untruthful, lie" (see lie (v.1)). "The form in -ar is probably in imitation of the refashioned forms such as scholar for scoler and pillar for piler" [Barnhart]. A different formation yielded Dutch leugenaar, Old High German luginari, German Lügner, Danish lögner.
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oath (n.)

Middle English oth, from Old English "judicial swearing, solemn appeal (to deity, sacred relics, etc.), in witness of truth or a promise," from Proto-Germanic *aithaz (source also of Old Norse eiðr, Swedish ed, Old Saxon, Old Frisian eth, Middle Dutch eet, Dutch eed, German eid, Gothic aiþs "oath"), from PIE *oi-to- "an oath" (source also of Old Irish oeth "oath"). Common to Celtic and Germanic, possibly a loan-word from one to the other, but the history is obscure and it may ultimately be non-Indo-European. In reference to careless invocations of divinity, from late Old English.

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arbitrator (n.)
"person chosen by opposite parties to decide some point at issue between them," early 15c., from Late Latin arbitrator "a spectator, hearer, witness; a judge," agent noun from past participle stem of arbitrari "be of an opinion, give a decision," from arbiter "a judge, umpire, mediator" (see arbiter).

The legal form of popular arbiter. In modern usage, an arbiter makes decisions of his own accord and is accountable to no one but himself; an arbitrator decides issues referred to him by the parties. "It is often the practice to appoint two or more arbitrators, with an umpire, chosen usually by them, as final referee" [OED].
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