I must be feeling tired again.
Tire isn’t only a word for how you feel, it’s also a word that means what you put on a vehicle. And they’re not related. Like, even a little. Vehicle tires actually come from the word attire (boy is that a long story for another post). The other tire, the one where you just want to sleep, is actually harder to pin down. It’s thought to be from the Proto Germanic teuzon, which is from the Proto Indo European deu-, to lack or be wanting. I guess I can see that. To be tired is to lack energy, right?
And now for another word that has multiple very different meanings, although these ones are at least related. Exhaust showed up in the sixteenth century, but it didn’t mean gas waste until the nineteenth century, and back then it referred to steam engines (I’m guessing they didn’t use it that way earlier because they didn’t have engines :P). Originally, exhaust just meant to use up, so I guess an exhaust was a by-product of what was being used up. Anyway, it came from the classical Latin exhaustus, drained, from the verb exhaurire, to drain. The prefix ex- means off and haurire also means drain, generally of water, and is from the Proto Indo European heusio-, to scoop. Basically the word went from literal to metaphorical in two different ways.
Weary comes from the Old English werig, tired, and it’s from the Proto Germanic worigaz, but after that it’s unknown. But what about the word wear, like one would wear out something? Ha ha. No. Not even a little. That’s right, to wear something out has nothing to do with being weary. It actually has to do with clothes. Clothes—or wear—are gradually damaged over time. They wear out. And that’s where we get that from.
Okay, let’s see what wild ride this one takes us on. Fatigue showed up in the mid seventeenth century from the French fatigue, which just means tired. It comes from the classical Latin fatigare, to exhaust, which is related to the Old Latin fatis, and before that we don’t know. As to why fatigues means a military uniform, well, when it first started being used in a military sense, it actually meant extra duties of a soldier, and I’m guessing that the extra duties were supposed to wear you out. That gave way to uniforms being called fatigue dress in the nineteenth century, and that’s why we have fatigues.
Wow. This one was weird.
Tony Jebson’s page on the Origins of Old English