Etymology
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mysterious (adj.)

1610s, "full of mystery, obscure, not revealed or explained," from Latin mysterium (see mystery (n.1)) + -ous. Related: Mysteriously; mysteriousness. Earlier in same sense was mysterial (early 15c.), from Late Latin mysterialis.

Mysterious is the most common word for that which is unknown and excites curiosity and perhaps awe; the word is sometimes used where mystic would be more precise. Mystic is especially used of that which has been designed to excite and baffle curiosity, involving meanings in signs, rites, etc., but not with sufficient plainness to be understood by any but the initiated. [Century Dictionary]
God moves in a mysterious way,
His wonders to perform;
He plants his footsteps in the sea,
And rides upon the storm
[Cowper, from the "Olney Hymns," 1779]

Related: Mysteriously; mysteriousness.

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cryptic (adj.)

1630s, "hidden, occult, mystical," from Late Latin crypticus, from Greek kryptikos "fit for concealing," from kryptos "hidden" (see crypt). Meaning "mysterious, enigmatic" is attested by 1920. Related: Cryptically.

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mystify (v.)

1798, "to make obscure, obscure the meaning of;" 1814, "perplex purposely," from French mystifier (1772), a verb formed irregularly from mystique "mysterious" (see mystic (adj.)) + -fier "to make" (see -fy). Related: Mystified; mystifying.

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inscrutable (adj.)
"that cannot be discovered by searching, mysterious," c. 1500, from Late Latin inscrutabilis, from in- "not, opposite of" (see in- (1)) + *scrutabilis, from scrutari "examine, ransack" (see scrutiny). Related: Inscrutably; inscrutableness.
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dido (n.)

"prank, caper," 1792, slang, perhaps from the name of the legendary Carthaginian queen in the "Aeneid." Usually in phrase to cut didoes. Century Dictionary repeats a story that attributes it to her having made a bargain for as much land as could be covered by a hide, then cutting the hide into a long, thin strip so as to enclose a large tract, but this is not in the early references to the term, which regard its origin as mysterious.

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mystic (adj.)

late 14c., mistike, "spiritually allegorical, pertaining to mysteries of faith," from Old French mistique "mysterious, full of mystery" (14c.), or directly from Latin mysticus "mystical, mystic, of secret rites" (source also of Italian mistico, Spanish mistico), from Greek mystikos "secret, mystic, connected with the mysteries," from mystes "one who has been initiated" (see mystery (n.1)).

Meaning "pertaining to occult practices or ancient religions" is recorded by 1610s. That of "hidden from or obscure to human knowledge or comprehension" is by 1630s.

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spatchcock 

in cookery, denoting a method of grilling a game bird after splitting it open along the spine and laying it flat; a word of obscure origin.

It originated in Ireland in the late eighteenth century as a noun, referring to the bird thus dispatched, and indeed it may have been based on the verb dispatch, with the addition of cock. Another probable influence is the earlier spitchcock, a word of mysterious origin denoting similar treatment meted out to eels and other fish. [Ayto, "Diner's Dictionary"]
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jinx (n.)

1911, American English, originally baseball slang; perhaps ultimately from jyng "a charm, a spell" (17c.), originally "wryneck" (also jynx), a bird used in witchcraft and divination, from Latin iynx "wryneck," from Greek iynx. Jynx was used in English as "a charm or spell" from 1690s.

Most mysterious of all in the psychics of baseball is the "jinx," that peculiar "hoodoo" which affects, at times, a man, at other times a whole team. Let a man begin to think that there is a "jinx" about, and he is done for for the time being. ["Technical World Magazine," 1911]

 The verb is 1912 in American English, from the noun. Related: Jinxed; jinxing. 

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mesmerism (n.)

"the doctrine that one person can exercise influence over the will and nervous system of another and produce certain phenomena by virtue of a supposed emanation called animal magnetism," 1798, from French mesmérisme, named for Franz Anton Mesmer (1734-1815), Austrian physician who developed a theory of animal magnetism and a mysterious body fluid which allows one person to hypnotize another and propounded it in 1778 in Paris. The word, if still used is practically synonymous with hypnotism or artificial somnambulism. Another similar word for the same effect was braidism. An old term for "hypnotic suggestion" was mesmeric promise. Related: Mesmerist

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parapsychology (n.)

"the study of phenomena outside the sphere of orthodox psychology," by 1923, from German para-psychologie; see para- (1) "beside" + psychology. Related: Parapsychological.

Similarly, [Prof. Hans Driesch] includes under "parapsychology" such phenomena as telepathy and clairvoyance, which he regards as mere extensions from ordinary mental phenomena, rather than as fundamentally different processes. He believes that the same orderly process by which unclassified and diverse processes have been systematized,—alchemy becoming chemistry, astrology becoming astronomy,—is at work now,—to make, in place of the mysterious tradition of Occultism, a science which will really be an extension from scientific psychology and biology. ["Journal of the American Society for Psychical Research," April 1923]
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