Etymology
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quadratic (adj.)

1650s, "square," with -ic + obsolete quadrate "a square; a group of four things" (late 14c.), from Latin quadratum, noun use of neuter adjective quadratus "square, squared," past participle of quadrare "to square, make square; put in order," related to quadrus "a square," quattuor "four" (from PIE root *kwetwer- "four"). In mathematics by 1660s; the algebraic quadratic equations (1680s) are so called because they involve the square and no higher power of x.

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indebted (adj.)
late 14c., endetted "owing money, liable for borrowed money," past participle of endetten "to indebt, oblige," from Old French endeter "to involve in debt, run into debt," from en- "in" (from PIE root *en "in") + dete "debt" (see debt). Figurative sense of "under obligation for favors or services" first attested 1560s. Spelling re-Latinized in English from 16c. The verb indebt is now rare or obsolete. Related: Indebtedness. Latin indebitus meant "not owed, not due."
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tackle (v.)
mid-14c., "entangle, involve," from tackle (n.). Sense of "to furnish (a ship) with tackles" is from c. 1400; meaning "to harness a horse" is recorded from 1714. The meaning "lay hold of, come to grips with, attack" is attested from 1828, described by Webster that year as "a common popular use of the word in New England, though not elegant;" figurative sense of "try to deal with" (a task or problem) is from 1840. The verb in the sporting sense first recorded 1867, "to seize and stop." Related: Tackled; tackling.
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*bher- (2)

Proto-Indo-European root meaning "bright; brown" (the sense connection might involve polished wooden objects).

It forms all or part of: Barnard; bear (n.) "large carnivorous or omnivorous mammal of the family Ursidae;" beaver (n.1) "large amphibious quadruped rodent of the genus Castor;" berserk; brown; Bruin; brunet; brunette; burnish.

It is the hypothetical source of/evidence for its existence is provided by: Old English brun "dark, dusky;" Lithuanian bėras "brown;" Greek phrynos "toad," literally "the brown animal."

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technical (adj.)

1610s, "skilled in a particular art or subject," formed in English from technic + -al (1), or in part from Greek tekhnikos "of art; systematic," in reference to persons "skillful, artistic," from tekhnē "art, skill, craft" (see techno-).

The sense narrowed to "having to do with the mechanical arts" (1727). Basketball technical foul (one which does not involve contact between opponents) is recorded from 1934. Boxing technical knock-out (one in which the loser is not knocked out) is recorded from 1921; abbreviation TKO is from 1940s. Technical difficulty is from 1805.

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rebec (n.)

small medieval three-stringed musical instrument with a pear-shaped sound box, played with a bow, early 15c., rebekke, from Old French rebec (15c.), an unexplained alteration (perhaps somehow influenced by bec "beak") of ribabe (13c.), which is ultimately from Arabic rebab.

Compare Old Provençal rebec, also, with random alterations, Middle English ribibe (c. 1400), ribible (early 14c.), Italian ribeca, ribebla, Portuguese arrabil, Spanish rabel. The same word also was used disparagingly for "old woman, crone," but the connection is unclear and it might involve the name Rebecca.

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embroil (v.)
c. 1600, "throw into disorder," from French embrouillier "entangle, confuse, embroil" (cognate of Italian imbrogliare), from assimilated form of en- "in" (see en- (1)) + brouiller "confuse," from Old French brooillier "to mix, mingle," figuratively "to have sexual intercourse" (13c., Modern French brouiller), perhaps from breu, bro "stock, broth, brew," from Frankish or another Germanic source (compare Old High German brod "broth"), from PIE root *bhreu- "to boil, bubble, effervesce, burn." Compare broil (v.2). Sense of "involve in a quarrel" is first attested c. 1610. Related: Embroiled; embroiling. Embrangle "mix confusedly" is from 1660s.
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intrigue (v.)

1610s, "to trick, deceive, cheat," from French intriguer (16c.), from Italian intrigare "to plot, meddle; perplex, puzzle," from Latin intricare "to entangle, perplex, embarrass" (see intricate).

Meaning "to plot or scheme" is recorded by 1714. That of "to excite curiosity" is from 1894 (OED calls this use "A modern gallicism"). It also could mean "carry on a clandestine or illicit sexual relationship" (1650s). The word appears earlier in English as entriken "entangle, ensnare; involve in perplexity, embarrass" (late 14c.), from Old French entrique or directly from the Latin verb. Related: Intrigued; intriguer; intriguing. Dutch intrigueren, German intriguiren are from French.

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self-involved (adj.)

"wrapped up in oneself or one's thoughts," 1812, from self- + involved.

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perplex (v.)

1590s, "embarrass, puzzle, bewilder, fill (someone) with uncertainty," evidently a back-formation from perplexed, a variant of the adjective perplex (late 14c.), "perplexed, puzzled, bewildered," from Latin perplexus "involved, confused, intricate;" but Latin had no corresponding verb *perplectere. The Latin compound would be per "through" (from PIE root *per- (1) "forward," hence "through") + plexus "entangled," past participle of plectere "to twine, braid, fold" (from suffixed form of PIE root *plek- "to plait").

The form of the English adjective began to shift to perplexed by late 15c., probably to conform to other past-participle adjectives, and the adjective perplex became obsolete from 17c. The verb is the latest attested of the group. The sense of "make intricate, involve, entangle, make difficult to be understood" is from 1610s. Related: Perplexing, which well describes the history of the word; perplexingly.

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