英和和英

語源

Popularized by Donald Rumsfeld in 2002, though used much earlier.

名詞

unknown unknown (plural unknown unknowns)

1. An uncertainty of unknown magnitude, consequence, structure, and probability characteristics, possibly with completely unsuspected existence; something that we don't know that we don't know.
   • 1970, United States Congress. Senate. Committee on the Judiciary. Subcommittee on Antitrust and Monopoly, Competition in Defense Procurement – 1969: Hearing, Ninety-first Congress, page 166:

     This means there are technical unknowns, unknown unknowns, and technical uncertainties in the contract.

   • 2002 February 12, Donald Rumsfeld, “Defense.gov News Transcript: DoD News Briefing – Secretary Rumsfeld and Gen. Myers, United States Department of Defense (defense.gov)”, in Defense.gov Transcript Archive‎, archived from the original on 10 August 2016:

     Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones.

   • 2014 January 29, Kenneth Chang, “Beings not made for space: After years of missions, health problems of astronauts elude doctors”, in International New York Times‎, page 7:

     NASA officials often talk about the "unknown unknowns" – the unforeseen problems that catch them by surprise.

   • 2026 April 15, Christian Wolmar, “Public deserve answers on overdue HS2 reset”, in RAIL, number 1059, page 45:

     But there are far more unknown unknowns.

同意語

• unk-unk

関連する語

• known known
• known unknown
• unknown known

参考

• a little knowledge is a dangerous thing