There’s been a long and fascinating conversation on the listserv of the American Dialect Society about fictional materials and their inclusion (or, more frequently, non-inclusion) in dictionaries, which led me to discover that the OED has included both unobtainium and impervium recently. Unobtainium is primarily in non-SF use, but impervium is almost exclusive to SF.
It dates (to current knowledge, anyway) to Philip Nowlan’s old Buck Rogers comic strip of Dec. 18, 1932, and is still in use today (the OED’s last citation is from Wil McCarthy’s 2005 novel To Crush the Moon). But it’s the intermediate cites that I find particularly interesting. The first to catch my eye was a clearly non-fictional use from The Journal of Nuclear Materials in 1989:
The CeS crucibles that we had developed were found to be so highly resistant to attack..that we thought the ‘Impervium’ crucibles could contain any molten metals.
A little poking about suggests that this was a republished version of this conference paper (pdf) by Leo Brewer, discussing crucibles they had devised from the compound CeS, a substance they dubbed “impervium,” for the Manhattan Project around 1942, just a decade after Nowlan’s coinage. Curious, I tried to find out what this compound is (“cerium sulfmumble” is what my stunning recollection of AP chemistry tells me), but I found pretty much squat. So
The other citation that caught my fancy was from Poetry magazine. Now, there’s a long history of speculative poetry, but it mostly finds publication in SF publications, so I was very surprised to see what appeared to be an SFnal citation from Poetry. The citation wasn’t clear enough for me to tell whether it was a literal or figurative usage, or really, much at all, so I thought I’d see what I could find out about the poem. The OED’s editorial policy is not to cite authors or titles of shorter works appearing in periodicals or anthologies, so there wasn’t much to go on (I understand this decision, especially the space constraints of the print editions, but I also think it’s too bad). Fortunately, Poetry seems to have its entire back catalog (or at least enough of it to include the relevant issue, Sept. 1957) free online. The poem in is “The Man from the Top of the Mind” by David Waggoner, and is, in fact, pure speculative poetry.