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a riddle, wrapped in a mystery, inside an enigma

That which is so dense and secretive as to be totally indecipherable or impossible to foretell. It is from a line used by Winston Churchill to describe the intentions and interests of Russia in 1939: "I cannot forecast to you the action of Russia. It is a riddle, wrapped in a mystery, inside an enigma; but perhaps there is a key. That key is Russian national interest." Many versions, variations, and appropriations of the quote, its structure, and its meaning have since been in use. Political campaigns make my head hurt. They're just a riddle, wrapped in a mystery, inside an enigma.
See also: enigma, inside, wrap

a mystery to (one)

Something that is difficult to understand. Why she walked out in such a huff this morning is a mystery to me! She was acting normally before that. It was a mystery to scientists where the birds migrated to until they banded some of them and tracked their movement.
See also: mystery

be another of life's great mysteries

To be difficult to understand or decipher. This phrase is often humorously applied to unimportant things. The living cannot truly understand death—it's another of life's great mysteries. Why dogs and cats hate each other is another of life's great mysteries.
See also: another, great, mystery, of

mystery meat

n. any unidentified meat. (Collegiate.) There are no hints as to what this mystery meat is—except its strange pinkish color.
See also: meat, mystery
References in classic literature ?
Your words are a mystery, too," returned the young lady.
In the middle of the hall, opposite the great door, a platform of gold brocade, placed against the wall, a special entrance to which had been effected through a window in the corridor of the gold chamber, had been erected for the Flemish emissaries and the other great personages invited to the presentation of the mystery play.
No, that was the babe the book speaks of--and the mystery of my origin is deeper than before, for I have thought much of late of the possibility of that cabin having been my birthplace.
When von Horn returned to the court of mystery, he narrated to Professor Maxon the gist of his conversation with Virginia, wishing to forestall anything which the girl might say to her father that would give him an impression that von Horn had been talking more than he should.
In the devil devil houses, where, before the face of mystery men and women crawled in fear and trembling, he walked stiff-legged and bristling; for fresh heads were suspended there-- heads his eyes and keen nostrils identified as those of once living blacks he had known on board the Arangi.
He has an inbred capacity for reading the riddle the right way in cases of mystery, great or small.
Mystery in the position of a lodger carries with it--what shall I say?
The breezes whispered strange secrets of elf-haunted glens, and the hollows where the ferns grew were brimmed with mystery and romance.
Whatever the mystery might be, he was plainly embarrassed by being called upon to reveal it at a moment's notice.
The Mystery Plays seem to have reached their greatest popularity in the fourteenth and fifteenth centuries.
Murat, Joachim, Prince The Vendetta The Gondreville Mystery Colonel Chabert Domestic Peace
The one unexplained mystery was the mystery of Launce's conduct in permitting his wife to return to her father's house.
She censured her, not for disapproving of the engagement, but for throwing over her disapproval a veil of mystery.
Because of the mystery which shrouded it, the case of The Yellow Room was certain to fascinate so theatrical a mind.
In fact, I remember the placid exaltation with which I took up my position on the forward upper deck, directly beneath the pilot-house, and allowed the mystery of the fog to lay hold of my imagination.