Nigger in the woodpile

Nigger in the woodpile or nigger in the fence is a figure of speech originating in the United States meaning "some fact of considerable importance that is not disclosed—something suspicious or wrong".
Commonly used in the late 19th and early 20th centuries, its usage has since declined, and use of the phrase by public figures has often been criticised due to the extreme offensiveness of the term "nigger".
Origin.
Both the "fence" and "woodpile" variants developed about the same time in the period of 1840–50, when the Underground Railroad was flourishing. The evidence is slight, but it is presumed that they were derived from actual instances of the concealment of fugitive slaves in their flight north under piles of firewood or within hiding places in stone walls. Another possible origin comes from the practice of transporting pulpwood on special railroad cars. In the era of slavery, the pulpwood cars were built with an outer frame with the wood being stacked inside in moderately neat rows and stacks. However, given the nature of the cars, it was possible to smuggle persons in the pile itself, possibly giving rise to the term.
Usage.
An American film comedy titled "A Nigger in the Woodpile" was released in 1904, and the idiom was common in literature and film during the 1920s and 1930s. Examples include the original 1927 version of the Hardy Boys book "The House on the Cliff" (pg. 77), where Frank Hardy uses the expression (removed when the story was revised in 1959), and the old-time band Skillet Lickers recording a song called "Nigger in the Woodpile" in 1930.
Dr. Seuss used the term in a 1929 cartoon "Cross-Section of The World's Most Prosperous Department Store", wherein customers browse through a department store looking for items to make their lives more difficult. The panels show a series of scenarios based on popular figures of speech: a man with a net trying to catch a fly for his ointment, another looking at monkey wrenches to throw into his machinery, one examining haystacks with matching needles, and finally a man looking at a selection of people drawn with stereotypical black features for his woodpile.
The author Zane Grey's 1921 novel "The Mysterious Rider" uses the expression at least twice throughout the story to explain a situation in which facts were purposefully omitted. In the 1929 RKO film "Street Girl," the phrase is spoken by Joseph Cawthorn, but it has been erased from the print that Turner Classic Movies shows.
In the 1930 pre-Code comedy "Not So Dumb", Marion Davies consistently and constantly convolutes common idioms and expressions. After finally finding misplaced billiard balls that she had used as darning eggs, she proudly exclaims, "I just knew there was a woodpile in the nigger when I couldn't find 'em."
A visual gag in the Looney Tunes cartoon "Porky's Railroad" from 1937 refers to the phrase.
The phrase is also used in "The Razor's Edge" by Somerset Maugham. One of the American characters, on the brink of closing a business deal, says to the narrator, "I'll fly down to Texas to give the outfit the once-over, and you bet I'll keep my eyes peeled for a nigger in the woodpile before I cough up any ... dough."
In Chapter 3 of "Absalom, Absalom", William Faulkner uses the phrase when referring to the success of a cotton plantation: "...some among his fellow citizens who believed even yet that there was a nigger in the woodpile somewhere."
The British mystery writer Dick Francis used it in chapter 18 of his first novel, 1962's Dead Cert 
Computer scientist Edsger W. Dijkstra uses the phrase in a published reply to referees ca 1975.
In the book "Your Health: A Corrective System of Exercising that Revolutionizes the Entire Field of Physical Education", by Joseph H. Pilates in 1934, page 18 writes, "This is the 'Nigger in the wood pile'."
Agatha Christie used the phrase as the title of chapter 18 of the 1937 Hercule Poirot novel "Dumb Witness", which was later published in the U.S. as "Poirot Loses a Client". The chapter was later retitled "A Cuckoo in the Nest". A character also uses the phrase in Chapter 22 of her 1953 book "After the Funeral". The phrase was also used by a character in early editions of Christie's novel "And Then There Were None" (originally released under the title "Ten Little Niggers"), but was changed in later editions to "There's a fly in the ointment". As late as 1952, in the novel "They Do It with Mirrors", published in the U.S. as "Murder with Mirrors," she has a character use the phrase. It appears in editions published as late as 1985. In her 1970 novel "Passenger to Frankfurt", she has a character use the phrase in chapter 23.
Erle Stanley Gardner also uses this phrase in several early Perry Mason mysteries, including "The Case of the Velvet Claws" (1933), "The Case of the Stuttering Bishop" (1936), and "The Case of the Substitute Face" (1938).
W. C. Fields used variations of this phrase in two of his films: In "You Can't Cheat an Honest Man" (1939) he said there was "an Ubangi in the fuel supply", and in "My Little Chickadee" (1940) he said there was "an Ethiopian in the fuel supply".
In the song, "This Could Be True", Pat Kirkwood and Graham Payn sing the phrase in Noël Coward's 1950 musical "Ace of Clubs".
Popular western author Louis L'Amour used a variant in "Crossfire Trail" (1954): "Now there seemed to be a larger African in the woodpile, or several of them."
Popular English music group Supertramp used the phrase in the lyrics of their song "Potter" from their 1971 album "Indelibly Stamped". Another English band, 10cc also used the phrase in their song "The Second Sitting for the Last Supper" from their album "The Original Soundtrack" from 1975.
The phrase declined in use during the 20th century, and now the occasional use of this phrase by public figures has often been followed by controversy and apology.
In July 2008, the leader of the Conservative Party, David Cameron, was urged to sack Conservative peer Lord Dixon-Smith, who said in the House of Lords that concerns about government housing legislation were "the nigger in the woodpile". Dixon-Smith said the phrase had "slipped out without my thinking", and that "It was common parlance when I was younger".
In July 2017, the phrase was again used by Conservative Party politician Anne Marie Morris who said that Brexit without a deal with the European Union was the "real nigger in the woodpile". She later said "The comment was totally unintentional. I apologise unreservedly for any offence caused." However, she was suspended the same day by the party's chief whip, on the orders of party leader, the prime minister, Theresa May. The Conservative Party whip was restored to Morris on 12 December 2017, one day before a crucial vote on the Brexit process. Although Morris voted with the Conservative Government, the Government was defeated by four votes.
Also in 2018 it was revealed that Irish race car driver and commentator Derek Daly had used the phrase in a radio interview in May 1983. Daly explained he was a foreign driver now in America, driving for an American team, with an American crew, and with an American sponsor—and that if things did not go well, he would be the only nigger in the woodpile. His comment caused an immediate uproar from people listening in Gasoline Alley as they warned him of the volatility of that word. Daly apologized and said the phrase had been an Irish colloquialism, and was not intended as a racial slur. Once it was revealed, Derek lost his commentator job. His son, who had not been born at the time the comments were made, also lost his sponsor for the weekend.
In 2019, the Australian Communications and Media Authority (ACMA) ruled that radio station 2GB breached the Commercial Radio Code of Practice when the broadcaster Alan Jones used a "racially charged phrase" during a segment in 2018. ACMA received numerous complaints after Jones used the controversial phrase in August 2018, while discussing the looming second Liberal Party of Australia leadership spill. "The nigger in the woodpile here, if one can use that expression – and I'm not going to yield to people who tell us that certain words in the language are forbidden – the person who's playing hard to get is Mathias Cormann," Jones told listeners. ACMA found that, while the phrase was widely considered racist, its use in the broadcast didn't likely incite "hatred", "serious contempt" or "severe ridicule". 2GB's management agreed the term will not be used on-air again.
In November 2019, a Downing Street aide alleged that Prince Andrew, Duke of York had used the phrase during a trade meeting.
In June 2020, a City Councillor in Taupo, New Zealand was subject to official complaints and a code of conduct investigation after using the phrase in a council meeting.