Take the plural angle. Measles and mumps are both reasonably old words, Middle English in one case and Early Modern in the other. More interestingly, both were plurals with s-less singulars. The vapors of course goes back to vapor, with its quaint-sound medical underpinnings. So, the older ones settled out as plurals, new ones have been created as plurals.
I wrote the above yesterday morning and dashed off to a monstrously long day at work, only to later find an email from a man who's always a couple of steps ahead, Ben Zimmer,* passing on a pile of excellent OED data. I've appended his whole email below. (I often cite Merriam-Webster when I'm in a hurry because I've got quicker access to it.) And while we're on comments: hh has an excellent comment calling attention to a 2001 squib in Linguistic Inquiry by Norvin Richards on "An idiomatic argument for lexical decomposition." I had entirely missed this little bit of data in that big discussion.
Semantically, note that we're not looking at the most serious diseases in the early set — plague, black death, the big C are singular, and diabetes ends in an s but it's definitely singular for me. Some of the old quotes on the vapors or on vapor do sound pretty bleak — Shakespeare uses it to good effect. Maybe that made it easier to build these humorous idioms?
The heebie-jeebies (I'm starting to like how it sounds, long about now) has a tangle of connections that is even denser: Phonoloblog's Eric Baković had this on partial labial reduplication, building on a LINGUIST query and summary, here. Heebie-jeebies doesn't show up, but look at some of the many h- + b- pairs discussed in one or both places:
- hubble bubble (>hubbub?)
- honey bunny
- hurly burly
1762 SMOLLETT Sir L. Greaves vii, I would there was a blister on this plaguy tongue of mine for making such a hollo-ballo.Metrically, we've had a few interesting reductions, of course, but that's another topic. And look at a few of the h- + p- cases:
- higgledy piggledy
- hodge podge
- hocus pocus
- hanky panky
*If you haven't read Ben's piece on National Dictionary Day, you're the last person who can read English with an internet connection … click here and get that off your record.
Appendix: The Zimmer Report
This is a little hard to search for in the full-text OED, but one way to find examples is to search on "fit of the", which turns up:Image from here.
fit of the blues 1807
fit of the glooms c1808
fit of the sulks 1824
fit of the 'clevers' 1826
fit of the shakes 1837
fit of the giggles 1881
fit of the shakes 1884
fit of the dismals 1893
fit of the slows 1927
fit of the uglies 1939
Those last two also go back to the 19th cent. outside of the "fit" frame: "the slows" ("an imaginary disease or ailment accounting for slowness") from 1843 and "the uglies" ("depression, bad temper") from 1846.
Still looking for more 18th cent. examples other than "the blues/blue devils". There's "the horrors" ("a fit of horror or extreme depression; spec. such as occurs in delirium tremens") from 1768, but that originally appeared as "in the horrors". Cites with "have/get/give the horrors" don't show up until the 19th cent. Similar story with "the mournfuls" (1794). Here's the earliest "get the Xs" I've found so far:
c1750 M. PALMER Dialogue in Devonshire Dial. (1837) 5 A call'd her a purting glum-pot, zed her'd got the mulligrubs.
"Mulligrubs" ("a state or fit of depression; low spirits; also: a bad temper or mood"), like "mubble-fubbles", goes back to the late 16th cent., but chiefly in the construction "in one's Xs".
One last example to brighten your day:
[Fantastic formation on COLIC n. and WOBBLE n.] A disordered state of the stomach characterized by rumbling in the intestines; diarrhoea with stomach-ache; hence gen. indisposition, 'butterflies in the stomach', a state of nervous fear. (In quot. 1853 used nonsensically.) 1823 EGAN Grose's Dict. Vulgar T., Collywobbles, the gripes. 1841 Punch 9 Oct. 154/1 To..keep him from getting the collywobbles in his pandenoodles. 1853 'C. BEDE' Verdant Green I. viii, A touch of the mulligrubs in your collywobbles? 1901 F. T. BULLEN Sack of Shakings 308 He laughingly excused himself on the ground that his songs were calculated to give a white man collywobbles. 1959 I. & P. OPIE Lore & Lang. Schoolch. x. 185 He is a 'funk'..or has 'got the collywobbles'.