So we’ve done slitheries and creepy crawlies. Now it’s time for the tiniest killer of all: disease.
Disease is pretty easy since it’s just dis- + ease. It showed up in the early fourteenth century meaning discomfort or inconvenience rather than an illness (although an illness certainly is a discomfort and an inconvenience) before taking on its modern meaning at the end of the century. It comes from the Old French desaise, which had meanings from discomfort to misfortune to disease. The prefix dis- means lack of or not, and ease is…well, come on, you know this. Makes sense, right? A lack of ease certainly sounds like what a disease does to you.
Sick comes from the Old English seoc, which is pretty much just sick, and before that, the Proto Germanic seukaz. As to where it came from or when exactly it showed up…yeah, no one knows. You should be expecting that by now.
Flu showed up in 1893 as a short form of influenza, which showed up earlier in 1743. It actually comes from Italian, where it’s also influenza and can mean the disease or, seriously, influence. Apparently in Italian, a disease is considered an influence of some higher power. So the flu is the flu because of superstitions. Of course.
Fever comes from the Old English fefor/fefer, fever. Before that, it was the classical Latin febris, fever, which is related to fovere, to heat. It’s possibly related to the Proto Indo European dhegh, burn, and possibly even the Sanskrit bhur, to be restless. Which is interesting, if it’s true, and raises a lot of questions as to where that F sound came from.
Plague showed up in the late fourteenth century as plage, which meant calamity or scourge before settling into its current epidemic definition. It comes from the Old French plage and Late Latin /classical Latin plaga, wound or stroke. It’s probably related to plangere, to lament by beating your breast (I could not make this stuff up) and the Greek plaga, blow (like a hit or strike), which can be traced all the way back to the Proto Indo European plak-, to strike or hit. So plagues strike figuratively, so we use the word for striking literally. All right. Moving on.
Pestilence first showed up in the early fourteenth century, coming from the Old French pestilence, which was a plague, and classical Latin pestilentia, also plague. Pestilentia comes from pestilentem, infected or noxious, and pestis, which means…pest. So pestilence is a pest.
Tony Jebson’s page on the Origins of Old English