Boris Johnson has been the subject of furious backlash after describing as "humbug" the idea that he should tone down his inflammatory language.
MP Paula Sherriff and others asked that he stop using terms such as "traitor" and betrayal", with the fate of Jo Cox, murdered by a member of the far right in 2016, raised as a warning.
Mr Johnson was dismissive, however, and reached into his wide vocabulary to palm off the criticism.
But what exactly does humbug mean when it's not preceded by a grumpy "bah"?
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Humbug has a few definitions, from the old-fashioned British mint-flavoured boiled sweet to an American term for false arrest.
Its primary meaning, according to the Oxford English Dictionary, however, is "deceptive or false talk or behaviour", as in "what you just said is humbug".
It can also be used as a verb, meaning to trick.
By extension it is also sometimes used to mean "nonsense".
The history of humbug
The word is a relatively recent coinage in linguistic terms, having first appeared in the middle of the 18th century.
The Oxford English Dictionary describes it as being of "unknown origin", although its first recorded appearance is thought to be in Ferdinando Killigrew's book The Universal Jester, published in 1754 at the latest, or more solidly in a book called The Student, published in 1751, in which is is described as fashionable slang.
But where did it come from? We don't exactly know.
One theory links it to the Italian phrase "uomo bugiardo", or "lying man", possibly in the early modern period at a point when there would have been a reasonably large amount of cultural exchange and literary influence from Italy.
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Another idea suggests that "hum" is a Norse word meaning "night", and bug, or bugge, means "apparitions".
The Encyclopaedia Britannica, in 1911, pointed to "Hamburg", the German city where counterfeit coins were minted to destabilise the British economy during the Napoleonic Wars - but the timescale does not fit.
Once it took off in Britain, it soon followed around Europe, where it's an accepted word in Germany, Hungary and further afield.
Though very much in vogue among the fashionable set in Georgian England, its most famous usage is decidedly Victorian.
Charles Dickens's A Christmas Carol features Ebeneezer Scrooge memorably crying "Bah! Humbug!" about Christmas, signalling his dislike of the eponymous festivities.
That's carried on into versions on stage and screen from the original novella to Disney's Scrooge McDuck and even the Muppets.
You might even hear it from a grumpy uncle from time to time if the festive spirit isn't taking hold, so associated is the phrase now with Christmas.
Scrooge says the phrase a number of times in the original book, but here's the first exchange with his more cheery nephew:
“A merry Christmas, uncle! God save you!” cried a cheerful voice. It was the voice of Scrooge’s nephew, who came upon him so quickly that this was the first intimation he had of his approach.
“Bah!” said Scrooge, “Humbug!”
He had so heated himself with rapid walking in the fog and frost, this nephew of Scrooge’s, that he was all in a glow; his face was ruddy and handsome; his eyes sparkled, and his breath smoked again.
“Christmas a humbug, uncle!” said Scrooge’s nephew. “You don’t mean that, I am sure?”
“I do,” said Scrooge. “Merry Christmas! What right have you to be merry? What reason have you to be merry? You’re poor enough.”
“Come, then,” returned the nephew gaily. “What right have you to be dismal? What reason have you to be morose? You’re rich enough.”
Scrooge, having no better answer ready on the spur of the moment, said, “Bah!” again; and followed it up with “Humbug.”
Humbug in Parliament
Boris Johnson is by no means the first person to describe something as humbug in the House of Commons, with records of its use going back as far as 1809.
It often appears in Hansard, the record of what's said in Parliament, as a one-word expression in reaction to another speaker, with or without the exclamation mark.
What's been humbug over the years? We've had everything from the debate regarding Irish home rule in 1912 to Aneurin Bevan making a pitch for working class democracy in 1934 to one John Bercow, then an MP, telling Tony Blair that his motto should have been "humbug, humbug, humbug" instead of "education, education, education".
Stephen Hesford, then the Labour MP for Wirral West, was asked to withdraw the term "humbug" in 2007 during a debate over the Finance Bill and responded: "May I withdraw humbug and replace it with something other than humbug that means humbug?"
On the advice of the Deputy Speaker, he went on to withdraw his whole remark.