There are any number of diseases one can catch, but have you ever noticed that two of them — mumps and measles — are plural? There’s not really any singular version; a mild case of mumps isn’t a “mump,” and there doesn’t seem to be any recorded case of anyone catching a “measle.”
There are some other similarities between “measles” and “mumps” — the words, that is, not the diseases. For one thing, if you go back far enough, both of them did have a singular version. You could find references to a single “mump” as recently as the late 1700s: “I pretended not to have been in the least tired, and put on such a rueful penitential mump as almost confounded them.” In those days, “mump” meant a facial expression, usually some sort of grimace. But it also meant swellings around your face, whether or not they were caused by the disease. In fact, the origin of “mump” has to do with an old German word, “mumpfen,” which meant chewing a too-large mouthful that made your cheeks swell out.
“Measles” also comes from a German word: “masel,” which was a red spot on the skin. The plural, in German, was “maselen,” but English seems to have adopted the singular version and pluralized it later, which is why English-speaking people catch “measles” instead of “measlen.”
Another version of “measles” is “measly,” which (sensibly enough) means somebody who has the measles. But it also means “of little value:” “The audacity to offer a measly hundred pounds or so for the discovery of a great crime!” (1864). It seems to be the same word, but nobody really knows how it acquired that second meaning. It probably happened sometime in the 1800s. Real etymologists might be able to figure it out, but since the reward is just a measly five bucks, nobody has bothered.
There’s another version of “mump” too, in “mumping.” That is (or was) the practice of policemen in England accepting favors: “Mumping free beer and a doughnut, well, that’s part of being a copper.” In the US, of course, it would typically be free coffee and a doughnut, but either way, we’re talking about a measly snack in exchange for a little extra consideration from the guys in blue. But wait, if they sometimes stuff the entire doughnut in their mouths, that might be why it was called “mumping” in the first place!
