How about a bunch of little words that we use all the time?
This comes from the Old English þis, which is just this where the th has its own letter. It’s thought to be from the North Sea Germanic pronoun tha-si-, which is a mix of the base word þa with an -s at the end. Once upon a time, this had tons of different forms, Masculine, Feminine, Neutral, and Plural, and of course in all the different tenses. I am just so glad we pared it down to one. How annoying would it be to have to conjugate twenty different forms for this???
That is from the Old English þaet, which is that much like we use it. It comes from the Proto Germanic that, from the Proto Indo European tod-, which is from the root word -to-. That also had masculine and feminine forms—the masculine form was actually se and the feminine seo, with an S! That with the th is actually the neutral form. And we should now all take a moment to thank Middle English for getting rid of gendered articles, because that is a stupid idea that makes things overcomplicated.
Next, we’re looking at the, which was þe in Old English. At least, that was one of its forms. In fact, þe was a later form, and earlier it was se—yes, the same se that came from. It’s from the Proto Indo European root so-, which you know is the origin of this and that. I guess that’s where all these words come from.
Now let’s look at some non-th words. At comes from the Old English aet, which is just at. It’s from the Proto Indo European ad-, to, near, or at, which is part of just so many words that start with a- or ad-. Anyway, that’s at. Fairly sensible origin, and almost completely unchanged in thousands of years. Impressive.
From comes from (ha!) the Old English fram, which is just from with a different vowel. It can be traced to the Proto Germanic fra, forward or away from (kind of contradictory there) and Proto Indo European pro-mo-… Seriously??? It’s actually from pro-, forward, and get this, frame is from the same place. Well, technically, frame is from the already mentioned Old English fram. As in, this is where the frame you use for pictures comes from. I am one hundred percent not making that up. The frame thing is something I’m going to have to get into another time because holy crap is that a journey.
Okay, let’s end with something more sensible. For comes from the Old English for, meaning… well, for. What were you expecting? It’s from the Proto Germanic fur and Proto Indo European per-, forward. Which is also where pro comes from.
Nothing much else to stay here. My mind is still reeling from the from/frame thing.
Tony Jebson’s page on the Origins of Old English