Etymology
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sworn 
past participle of swear; sworn enemies, those who have taken a vow of mutual hatred, is from c. 1600.
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celibate (adj.)

"unmarried, sworn to remain single," 1825, probably from celibate (n.) or from celibacy on the model of privacy/private, etc.

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jurat (n.)
also jurate, "one who has taken an oath," early 15c. (mid-14c. in Anglo-French), from Medieval Latin iuratus "sworn man," noun use of past participle of Latin iurare "to swear" (see jury (n.)). Meaning "official memorandum at the end of an affidavit" (showing when and before whom it was sworn) is from 1796, from Latin iuratum, noun use of the neuter past participle.
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fealty (n.)
c. 1300, feaute, from Old French feauté, earlier fealte, "loyalty, fidelity; homage sworn by a vassal to his overlord; faithfulness," from Latin fidelitatem (nominative fidelitas) "faithfulness, fidelity," from fidelis "loyal, faithful" (from PIE root *bheidh- "to trust, confide, persuade").
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wager (n.)
c. 1300, wajour "a promise, a vow, something pledged or sworn to;" also "a bet, a wager; stakes, something laid down as a bet," from Anglo-French wageure, Old North French wagiere (Old French gagiere, Modern French gageure) "pledge, security," from wagier "to pledge" (see wage (n.)).
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affidavit (n.)
"written declaration upon an oath," 1590s, from Medieval Latin affidavit, literally "he has stated on oath," third person singular perfective of affidare "to trust; to make an oath," from Latin ad "to" (see ad-) + fidare "to trust," from fidus "faithful," from PIE root *bheidh- "to trust, confide, persuade." So called from being the first word of sworn statements.
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Styx 
late 14c., the Greek river of the Underworld, literally "the Hateful," cognate with Greek stygos "hatred," stygnos "gloomy," from stygein "to hate, abominate," from PIE *stug-, extended form of root *steu- (1) "to push, stick, knock, beat." Oaths sworn by it were supremely binding and even the gods feared to break them. The adjective is Stygian.
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celibate (n.)

1610s, "state of celibacy" (especially as mandated to clergy in the Catholic church) from French célibat (16c.), from Latin caelibatus "state of being unmarried" (see celibacy). This was the only sense until early 19c.; the meaning "one who is sworn to celibacy" is from 1838. Other nouns in this sense were celibatarian, celibatist, celibian.

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jury (n.)

"set number of persons, selected according to law and sworn to determine the facts and truth of a case or charge submitted to them and render a verdict," early 14c. (late 12c. in Anglo-Latin), from Anglo-French and Old French juree (13c.), from Medieval Latin iurata "an oath, a judicial inquest, sworn body of men," noun use of fem. past participle of Latin iurare "to swear," from ius (genitive iuris) "law, an oath" (see jurist).

Meaning "body of persons chosen to award prizes at an exhibition" is from 1851. Grand jury attested from early 15c. in Anglo-French (le graund Jurre), literally "large," so called with reference to the number of its members (usually 12 to 23). Jury-box is from 1729; juryman from 1570s. Figurative phrase jury is still out "no decision has been made" is by 1903.

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ranger (n.)

late 14c. (early 14c. in surnames), "gamekeeper, sworn officer of a forest whose work is to walk through it and protect it," agent noun from range (v.). Attested from 1590s in the general sense of "a rover, a wanderer;" from 1660s in the sense of "man (often mounted) who polices an area." The elite U.S. combat unit is so called from 1942 (organized 1941).

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