Scrolling through my Facebook feed this morning (a chore I generally perform once a day), I found a series of posts from He Who Comments Here as ∅ under the heading “New students”; the relevant excerpts:
Today I used the word “parallelepiped” in class. I love good old geometry words. (I think that the phrase “good old geometry word” is one of those things I say a little too often when I’m teaching.) […]
By the way, at the blackboard I was clueless as to what the vowel between “parallel” and “piped” was — and I’m usually quite a good speller.
Also, I started wondering where the last part of that word came from. I was going to try to remember to look it up when I got home. No need: there was already an email from another student in the class who had already looked it up. This is one of the little gang who had me assigned as their first-year advisor. I knew he was a collector of arcane geographical knowledge, like myself, but I didn’t know that this applied to etymology, too.
It turns out that “epiped” means something like “plane surface”. Also, in the good old days this good old geometry word was pronounced “parallel-EP-iped”, whereas now we generally say “parallel-a-PIPE-ed”.
I had entirely forgotten the existence of this word, which I probably last heard in high school geometry class, and I too would have been clueless as to what the vowel between “parallel” and “piped” was; I am delighted with the etymology and accepting of the development of pronunciation away from the absurd-unless-you-know-Greek “parallel-EP-iped” to the more sensible “parallel-a-PIPE-ed” (though some people say “parallel-a-PIP-ed”). The OED (entry updated June 2005) has:
Pronunciation: Brit. /ˌparəlɛlᵻˈpʌɪpɛd/ , /ˌparəlɛlᵻˈpɪpɛd/ , U.S. /ˈˌpɛrəˌlɛləˈpaɪpᵻd/ , /ˈˌpɛrəˌlɛləˈpɪpᵻd/
Etymology: < post-classical Latin parallelepipedum (4th–5th cent.; also 5th–6th cent. in Boethius) or its etymon Hellenistic Greek παραλληλεπίπεδον parallelepipedon n. Compare French parallélépipède (1639; also parallelipipède (1762; attested earlier in Middle French as adjective (1570)). Compare earlier parallelepipedon n.
N.E.D. (1904) gives the pronunciation as (pærălelˌe·piped) /ˌpærəlɛlˈɛpɪpɛd/.
Oh, and if you were wondering, it’s “A solid figure whose faces are six parallelograms, of which opposite pairs are parallel; a prism whose base is a parallelogram.”