The meaning and the origins of "everything's gone pear-shaped."

Wikipedia confirms that yes, it does mean what you think - but the etymology is less certain:

The third meaning is mostly limited to the United Kingdom, Ireland and Australasia. It describes a situation that went awry, perhaps horribly wrong. A failed bank robbery, for example, could be said to have "gone pear-shaped". Less well known in the US it generated some media interest when British politician Margaret Thatcher used the phrase in front of the world's press at one of her first meetings with U.S. President Ronald Reagan, with many reporters being unsure of the meaning of the term. The origin for this use of the term is in dispute. The OED cites its origin as within the Royal Air Force; as of 2003 the earliest citation there is a quote in the 1983 book Air War South Atlantic. Others date it to the RAF in the 1940s, from pilots attempting to perform aerial manoeuvres such as loops. These are difficult to form perfectly, and are usually noticeably distorted—i.e., pear-shaped.

The OED entry (updated March 2003) for pear-shaped, adj. (paywalled), defines sense 3 as

colloquial (chiefly British, orig. R.A.F. slang). to go (also turn) pear-shaped: to go (badly) wrong, to go awry.

OED's earliest attestation is from 1983, in the context of the British response to the Argentine invasion of the Falkland Islands:

J. Ethell & A. Price Air War South Atlantic 158 There were two bangs very close together. The whole aircraft shook and things went 'pear-shaped' very quickly after that. The controls ceased to work, the nose started to go down.

I was unable to confirm any earlier use in the RAF than that attested in 1983.

A use in 1968 (The Post-Crescent, Appleton, Wisconsin, 28 Apr, p. 79; paywalled) attests the earlier appearance of the sense:

And the way the world (a big weather balloon that leaked) went pear-shaped during a performance of "Love Makes the World Go 'Round."

Slang use of 'to go (also turn) pear-shaped' with the meaning "to go wrong, to go awry" in the RAF during World War II may derive from reports such as this 1938 (paywalled) description of the sinking of the US Gunboat Panay (Star Tribune, Minneapolis, Minnesota, 01 Jan, p. 12):

 Then, from under the plane, a black dot appears...As it is darting toward you it becomes larger...Then there is a shape to it...A second later...it becomes a pear-shaped plummet, stream-lined for speed, trailing off in a fish-tail.
 Hell from heaven, this plummet is a roaring bomb.

Indeed, bombs and mines were frequently described in UK newspapers as 'pear-shaped' during the war.

 The mine, a large black pear-shaped object....

Newcastle Journal, 02 March 1940, p. 12 (paywalled).

It was a pear-shaped mine which when dropped from the air had a parachute attached to the "stalk" to deaden the shock of falling.

Belfast Telegraph, 02 March 1940, p. 7 (paywalled).

Examples of what is believed to be a new type of aeroplane bomb of enormous potency are being washed up...The bomb consists of a pear-shaped object three feet long and fifteen inches in diameter.

Liverpool Daily Post, 30 March 1940, p. 7 (paywalled).

In contrast to OED's derivation of 'to go pear-shaped' from RAF slang, Robert W. Holder, in How Not to Say What You Mean: a Dictionary of Euphemisms (Third Edition, 2002; originally published in 1987, revised for later editions) says this:

pear-shaped unsuccessful

Probably from the form of an analyst's graph, the use having started as jargon in financial circles. As with the fruit, the weight is at the lower end...

Holder provides an attestation of the variant "went pear-shaped" from the Daily Telegraph of 20 June 1997.

A common trauma unrelated to the shapes of bombs may contribute to the comparative frequency of 'to go pear-shaped', and so to other constructions on the same model, in contemporary speech. The trauma, male menopause, is described in a 1942 Arizona Republic article:

 One common symptom in men is the increase in weight, particularly in lower abdomen and often a loss of fat and muscle also about the chest and shoulders. Instead of the wide shoulders and narrow or medium hips, he becomes pear shaped in appearance.

Women, it appears, suffer from a similar problem. None other than Emily Post, in 1932 (a syndicated column; paywalled), remarks, with phrasing identical to a variant of the later, more abstract figurative expression, that

Precisely as one should take setting-up exercises every day to keep one's figure from going pear-shaped in the hips....

Newspapers reran Post's 1932 advice in 1941, and again in 1949. The same phrasing characterizes other quasi-literal uses in the 1960s:

...[a black-and-white television] has developed a variety of tube troubles in old age. The picture often tends to squish in at the top, broaden at the middle, and then becomes narrow and curvy toward the bottom....
 Well, a little aberration can be a devastating thing. What our TV did to thos 36-24-36 figures was bad enough to gladden the hearts of all overweight, over-thirty types.
 The pageant wasn't boring, Miss Alexander, it was (if you'll pardon the expression) a riot. Imagine those dolls coming on looking so peachy and then suddenly going pear-shaped!

Garden City Telegram (Garden City, Kansas) 16 Oct 1968, p. 4 (paywalled).

Diamonds may be a girl's best friend after her figure goes pear-shaped, but they can be next to worthless too....

The Californian (Salinas, California) 10 May 1969, p. 1 (paywalled).

Also worth noting is the occasional mention of the 'pear-shaped problem'. The mentions are ill-defined, but show up earlier, bracket Post's quasi-literal uses, and may be the noun progenitor or a sibling of the verb phrase. Here are some examples:

An average of one child a day is killed by automobiles in Greater New York, showing that speed regulations and rules of the road still afford a large, pear-shaped problem for those who must solve it.

The Atchison Daily Globe (Atchison, Kansas) 30 Jan 1913, p. 4 (paywalled).

Now Iverson runs a posture clinic here. He concentrates on children because he believes the answer to the nation's pear-shaped problem lies in correcting youngsters early.

Press and Sun-Bulletin (Binghamton, New York) 18 Aug 1950, p. 13 (paywalled).

"When one monkeys with Uncle Sam's security procedures, he's bound to have a large, pear-shaped problem on his hands," he continued.

The Hays Daily News (Hays, Kansas) 06 Jan 1972, p. 4 (paywalled).

All told, then, the absence of early direct primary source evidence for a British, RAF origin of 'to go pear-shaped', and the comparative abundance of evidence, in the form of identical phrasing, suggests an origin in the earlier quasi-literal expression of the sorry effects of aging on the human physique.

Jonathon Green, Chambers Slang Dictionary (2008) lists pear-shaped as a surprisingly recent slang coinage—certainly more recent than the 1940s/1950s period reported by The Phrase Finder and cited in Thursagen's answer. Here are the relevant entries from Green:

pear-shaped adj. {the image of a solid rectangle 'slipping down' into a pear shape, hence 'the bottom drops out'} {2000s} out of order, going badly or wrong.

go pear-shaped v. (also turn pear-shaped) {1990s+} of plans or schemes, to fail, to collapse.

I ran a series of exact-phrase searches for various related phrases at The British Newspaper Archive (a subscription service to which I am not a subscriber) to see what the earliest claimed matches are. Here's what the site delivered:

• "go pear-shaped": Newcastle Journal (July 3, 1992); Liverpool Echo (May 18, 1995); Liverpool Echo (November 16, 1996); Liverpool Echo (December 7, 1996); [Dublin] Irish Independent (March 5, 1997).

• "going pear-shaped": [Dublin] Irish Independent (June 14, 1997); [County Wexford] New Ross Standard (April 21, 1999); [Dublin] Sunday Tribune (April 25, 1999); [County Wexford] Wexford People (December 15, 1999); [Dublin] Evening Herald (December 30, 1999).

• "gone pear-shaped": Liverpool Echo (January 27, 1997); [Dublin] Evening Herald (May 1, 1997); [County Kerry] Kerryman (May 30, 1997); Liverpool Echo (December 17, 1998); Liverpool Echo (March 3, 1999).

• "went pear-shaped": [County Wicklow] Bray People (May 12, 1995); [County Wicklow] Bray People (September 14, 1995); [Dublin] Irish Independent (August 26, 1996); Liverpool Echo (May 31, 1997); [Dublin] Evening Herald (June 17, 1997).

• "turn pear-shaped": [Dublin] Irish Independent (November 6, 1999); [Dublin] Evening Herald (July 16, 2001); [Dublin] Sunday Independent (April 3, 2005); [Dublin] Evening Herald (May 14, 2005); [Dublin] Irish Independent (July 25, 2005).

• "turning pear-shaped": [Devon] Western Morning News (November 30, 1927); [Dublin] Sunday Tribune (December 13, 1998).

• "turned pear-shaped": [Dublin] Sunday Independent (December 15, 1996); Liverpool Echo (December 26, 1998); [Dublin] Evening Herald (June 27, 2005); [Dublin] Evening Herald (January 30, 2009).

Since I couldn't check to see how many of these matches are false positives, I have no idea how many (if any) are actual matches for the specified exact phrase; nor do I know whether the British Newspaper Archive's database of searchable newspapers from recent decades comprises more than a handful of publications.

Nevertheless, I think it is noteworthy that—aside from a highly suspect outlier from 1927—the claimed matches are all from 1992 or later. This puts the claimed matches from the British Newspaper Archive in harmony with Jonathon Green's assertion that "go [or turn] pear-shaped" dates to "1990s+." As circumstantial evidence goes, it's not terribly strong—but it is something.

Question 1: The history can be found in The Phrase Finder:

To go pear shaped is an expression used to indicate that a scheme has not been perfectly executed. The phrase seems to have originated in British English in the late 1940s or early 1950s. I have come across several suggested origins, but the best, for me, is related to training aircraft pilots. At some stage they are encouraged to try to fly loops - very difficult to make perfectly circular; often the trainee pilot's loops would go pear shaped.

author: James Briggs (May 11, 2000)