unk-unk
n.— «Aerospace-men have come down with a severe case of what they call the “unk-unks”—the “unknown unknowns.”» —“Aerospace: End of the Gravy Years” Time Mar. 9, 1970. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...
Cat hair may be something you brush off, but cat hair is also a slang term that means “money.” In the same way, cat beer isn’t alcoholic — some people use cat beer as a joking term for “milk.” And imagine walking on a...