Plain English speakers cover your ears - the once derided "unknown unknown" has been gaining currency and its latest advocate is British politician Jack Straw.
Can you repeat that please, Jack?
First it was mocked, then turned into poetry, now Donald Rumsfeld's convoluted syntax is being adopted on this side of the Atlantic.
Although Mr Rumsfeld did not invent the phrase "unknown unknowns" - it has long existed in US business and engineering circles - he planted it firmly in the public mind when talking about weapons of mass destruction in 2002.
The sentence which contained the phrase went on to earn Mr Rumsfeld the Plain English Campaign's annual Foot in Mouth award and led writer Hart Seely to repackage it as "existential poetry".
Yet despite this mocking, the term "unknown unknowns" has been quietly gaining support. Its latest advocate is Justice Secretary Jack Straw, who used it on the BBC's Today programme on Friday when questioned about the donations controversy engulfing Labour.
"To quote Don Rumsfeld," said Mr Straw, "for a long time this was an unknown unknown. The moment it became a known known, we got on to it."
He didn't elaborate but Mr Rumsfeld meant he was talking about revelations that were either anticipated (known unknowns) or completely unexpected (unknown unknowns).
The first recorded use of the term "unknown unknowns" was in the US engineering industry in 1969, says Jesse Sheidlower, editor-at-large of the Oxford English Dictionary, even abbreviated to "unk-unk".
Unk-unks - what we don't know we don't know
"Known unknowns are things we know we don't know, but unknowns are things we don't know we don't know and while we can't predict them because they're unknown unknowns, we're aware they're out there.
"Doing a multi-billion-dollar project, there are things you don't even know you don't know."
Although he was widely lampooned, Rumsfeld was not necessarily trying to mislead anyone, says Mr Sheidlower, just taking the phrases out of their normal context of use.
Fiona Douglas, a lecturer in English language at the University of Leeds, says the terms have growing popularity, and not just in politics.
"The terms do, on the surface, appear tautologous, but usage suggests that actually 'known knowns' and 'unknown unknowns' have carved out a semantic space for themselves. Those who use them do seem to find them in some way a useful addition to their linguistic repertoire."
But lexicographer Tony Thorne is less forgiving - saying Mr Straw's use of the phrase smacks of a politician on the defensive and deflecting blame.
"Linguists talk about the speaker's intent as opposed to the speaker's meaning. What they are really trying to say is 'we're not in control and we don't know what's going on and we're not going to be held responsible.'
"I'm surprised that Jack Straw would use that strategy because once Rumsfeld used it, it was discredited in many people's eyes."
It may sound "portentous" and "meaningful" says Mr Thorne, but it only works in business or military circles and giving it political use has risks attached.
"It's typical of politicians, they either use the short, brutal, unanswerable soundbite or the convoluted like a cantation, a magical mantra to bamboozle people. First you have to compute it. If you actually try to decipher it, it takes five minutes to work out."
But with phrases such as "bottom line" moving from the boardroom to the street, will we all soon been discussing "unknown unknowns"?
Only sarcastically, says Mr Thorne, because it does not fill what linguists call a "lexicon gap" in the English vocabulary.