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A borrowing from French, the exclamative phrase quel idiot! means: what an idiot!.
In this phrase (pronounced /kɛlidjo/), the noun idiot is masculine singular.
When the noun idiot is:
– masculine plural, the phrase is quels idiots! (pronounced /kɛlzidjo/);
– feminine singular, the phrase is quelle idiote! (pronounced /kɛlidjɔt/);
– feminine plural, the phrase is quelles idiotes! (pronounced /kɛlzidjɔt/).
This phrase occurs, for example, in a review of The Bloody English Women of the Maison Puce (Michael Joseph, 2001), by Jill Laurimore—review by Hester Lacey, published in The Independent on Sunday (London, England) of Sunday 22nd April 2001 [The Sunday Review: page 49, column 1]—after her divorce, Alice Barnes, an Englishwoman, has settled down in southern France:
Alice, frankly, is a bit of a drip—a few sandwiches short of a pique-nique. Her French is vraiment pathetique and she is amazed to find that, the south of France not being equatorial Africa, it actually gets quite chilly in the winter (she’s left all her warm coats behind in Bristol, quelle idiote).
—Cf. also the phrase quelle surprise!.
These are, in chronological order, the earliest occurrences of the exclamative phrase quel idiot! that I have found:
—Note: In most cases, this phrase occurs in French contexts or/and the speakers are French:
1-: From But Brioche!, one of “Phrynette’s Letters to Lonely Soldiers”, by Marthe Troly-Curtin, published in The Sketch (London, England) of Wednesday 18th April 1917 [page 49, column 2]—Phrynette, a French teenage girl, writes about her life in Britain; “the Imp” is the nickname of her niece, Germaine Tréville:
People’s sense of humour differs vastly. I am still trying to find a sparkle of wit in the “joke” I was supposed to enjoy a few days ago. I had been asked to a party—to last from evening till dawn. […] In spite of my fur coat, I froze on the way to my very marrow. It was one of those Polar spring nights of your island! […] We arrived at the house, benumbed, but faithful to the tryst; alas! only to find on the door a label couched thus—
“Party postponed.
Regrets.”
We stood on the doorstep puzzled and shivering. Suddenly the Imp exclaimed, “Quels Idiots!” (She was not referring to us.) “Why, it is the First of April!” And so it was.
But we ambled disconsolately, arm in arm, and singing sotto voce, “All dressed up and nowhere to go.”
2-: From Emile’s Hands, a short story by Dell Leigh, published in The Tatler (London, England) of Wednesday 4th March 1925 [page 412, column 1]—Emile Parienne, from Saint-Jean-Pied-de-Port, in south-western France, is a croupier in a French casino:
She was from the Basque country, his country. Clearly, without possibility of error, she was from the Pyrenees. She brought the sun and the scents and the tigerish somnolence of all that beloved world in with her as she advanced languidly towards his table from the cold marble vestibule. She carried all the sweets and desires, hates, and illicit enchantments of the Spanish-French pays on her deftly-tinted face, and in her nigger-brown eyes which swept over him in a cynically appraising glance, as they swept over all men. Yes, assuredly in her eyes—par Dieu, what eyes!—wherein tremendous import lay to Emile, though he knew it not then. It was when her eyes fell upon him in their swift travel from man’s face to man’s face, and paused a moment interrogatively, that Emile committed with a five-franc piece what was to him the blunder of years.
“Pah, quel imbecile!” he had chastised himself, “quel idiot!”
3-: From chapter 35 (set in Paris, France) of The Black Gale, a novel by the U.S. author Samuel Shellabarger (1888-1954), as published in The Border Cities Star (Windsor, Ontario, Canada) of Friday 4th December 1931 [Section 2: page 16, column 2]—in the following passage, Angele, a French woman, speaks to the main character of the novel, the U.S. artist Jacklin Baron:
Angele smiled. “I told him he couldn’t do better than imitate you; whereupon he invited Henri and me to the Carlton for supper. But afterward Henri made a scene, because I had told Levier that. Quel idiot!”
4-: From I Write As I Please (New York: Simon and Schuster, Inc., 1935), by the British journalist Walter Duranty (1884-1957) [chapter 18, page 226]—in the following passage, the speaker is “Rollin, the only French correspondent in Moscow at that time”, i.e., at the time of Lenin’s death, in January 1924:
“The divergence between Trotzky and Stalin is fundamental. I’ll admit that both of them are sincere, but now that Lenin has gone there is bound to be a clash between them. Until now I would have picked Trotzky to win. I know that he is more popular than Stalin and I thought he was much cleverer, but now I have begun to doubt it. My God, what an opportunity to miss! Achilles sulking in his tent. Quel idiot! As if he couldn’t understand that the whole strength of his position was his reputation with the masses as Lenin’s chief aide and supporter.”