Etymology
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mischief (n.)

c. 1300, "evil condition, misfortune; hardship, need, want; wickedness, wrongdoing, evil," from Old French meschief "misfortune, harm, trouble; annoyance, vexation" (12c., Modern French méchef), verbal noun from meschever "come or bring to grief, be unfortunate" (opposite of achieve), from mes- "badly" (see mis- (2)) + chever "happen, come to a head," from Vulgar Latin *capare "head," from Latin caput "head" (from PIE root *kaput- "head").

Meaning "harm or evil considered as the work of some agent or due to some cause" is from late 15c. Sense of "playful malice" is recorded by 1784. The meaning has softened with time; in Middle English to be full of mischief was to be miserable; to make mischief was "to result in misery."

Mischief Night in 19c. England was the eve of May Day and of Nov. 5, both major holidays, and perhaps the original point was pilfering for the next day's celebration and bonfire; but in Yorkshire, Scotland, and Ireland the night was Halloween. The useful Middle English verb mischieve (early 14c.), used by Skelton and Gavin Douglas, has, for some reason, fallen from currency.

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mischievous (adj.)

early 14c., "unfortunate, disastrous, miserably, wretchedly," probably from mischief + -ous. Sense of "playfully malicious or annoying" is attested by 1670s. "The stressing on the second syllable was common in literature till about 1700; it is now dialectal, vulgar, and jocular" [OED]. Related: Mischievously; mischievousness.

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mis- (2)

word-forming element of Latin origin (in mischief, miscreant, misadventure, misnomer, etc.), from Old French mes- "bad, badly, wrong, wrongly," from Vulgar Latin *minus-, from Latin minus "less" (from suffixed form of PIE root *mei- (2) "small"), which was not used as a prefix in Latin but in the Romanic languages was affixed to words as a depreciative or negative element. The form in French perhaps was influenced in Old French by *miss-, the Frankish (Germanic) form of mis- (1).

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*kaput- 
Proto-Indo-European root meaning "head."

It forms all or part of: achieve; behead; biceps; cabbage; cabochon; caddie; cadet; cap; cap-a-pie; cape (n.1) "garment;" cape (n.2) "promontory;" capital (adj.); capital (n.3) "head of a column or pillar;" capitate; capitation; capitulate; capitulation; capitulum; capo (n.1) "leader of a Mafia family;" capo (n.2) "pitch-altering device for a stringed instrument;" caprice; capsize; captain; cattle; caudillo; chapter; chef; chief; chieftain; corporal (n.); decapitate; decapitation; forehead; head; hetman; kaput; kerchief; mischief; occipital; precipice; precipitate; precipitation; recapitulate; recapitulation; sinciput; triceps.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kaput-; Latin caput "head;" Old English heafod, German Haupt, Gothic haubiþ "head."
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hob (n.)
"clown, prankster," short for hobgoblin (q.v.). Hence, to play (the) hob "make mischief" (by 1834).
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devilment (n.)

"trickery, roguishness, mischief, action befitting a devil," 1771; see devil + -ment.

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Ate 
Greek goddess or personification of infatuation and blundering mischief, from ate "damage, ruin; guilt; blindness, dazzlement, infatuation; penalty, fine," which is of uncertain origin.
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firebrand (n.)
also fire-brand, c. 1200, "piece of wood kindled at a fire, a piece of something burning," from fire (n.) + brand (n.). Used for spreading fire. Figurative sense of "one who kindles mischief or passions" is from late 14c.
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malefic (adj.)

"doing mischief, producing disaster or evil," 1650s, from Latin maleficus "wicked, vicious, criminal," from male "ill" (see mal-) + -ficus "making, doing," from combining form of facere "to make, do" (from PIE root *dhe- "to set, put"). Related: Malefical (1610s).

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Ralph 
masc. proper name, shortened from Radulf, from Old Norse Raðulfr (Old English Rædwulf), literally "wolf-counsel," from rað "counsel" (see read (n.)) + ulfr "wolf" (see wolf (n.)). The Century Dictionary also lists it as English printers' slang for "An alleged or imagined evil spirit who does mischief in a printing house."
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