"the act of extorting, the act or of wresting anything from a person by force, duress, menace, authority, or any undue exercise of power, oppressive or illegal exaction," c. 1300, from Latin extortionem (nominative extortio) "a twisting out, extorting," noun of action from past-participle stem of extorquere "wrench out, wrest away, to obtain by force," from ex "out" (see ex-) + torquere "to twist" (from PIE root *terkw- "to twist").

c. 1600, from Late Latin imminentia, from Latin imminentem (nominative imminens) "overhanging; impending," present participle of imminere "to overhang, lean towards," hence "be near to," also "threaten, menace, impend, be at hand, be about to happen," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + -minere "jut out," which is related to mons "hill" (from PIE root *men- (2) "to project"). 

1520s, from French imminent (14c.) and directly from Latin imminentem (nominative imminens) "overhanging; impending," present participle of imminere "to overhang, lean towards," hence "be near to," also "threaten, menace, impend, be at hand, be about to happen," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + -minere "jut out," which is related to mons "hill" (from PIE root *men- (2) "to project"). Related: Imminently.

Old English þreat "crowd, troop," also "oppression, coercion, menace," related to þreotan "to trouble, weary," from Proto-Germanic *thrautam (source also of Dutch verdrieten, German verdrießen "to vex"), from PIE *treud- "to push, press squeeze" (source also of Latin trudere "to press, thrust," Old Church Slavonic trudu "oppression," Middle Irish trott "quarrel, conflict," Middle Welsh cythrud "torture, torment, afflict"). Sense of "conditional declaration of hostile intention" was in Old English.

early 14c., "announce, make known in a formal manner" (a sense now obsolete), from Old French denoncier (12c., Modern French dénoncer) and directly from Latin denuntiare "to announce, proclaim; denounce, menace; command, order," from de- "down" + nuntiare "proclaim, announce," from nuntius "messenger" (from PIE root *neu- "to shout").

The negative sense in English developed (probably encouraged by other words in de-) via the meanings "proclaim as cursed, excommunicated, removed from office" (early 14c.); "formally or publicly threaten to do" (1630s); "declare or proclaim to be cursed, wicked, or evil" (1660s). The meaning "make formal or public accusation against, inform against, accuse" (especially in turning on one's co-conspirators) is from late 15c. Related: Denounced; denouncing.