Obviously nothing will be as great as last week’s union/onion revelation, but that doesn’t mean we don’t etymologize words.
So. Truth. I don’t have a date for it, but it meant “something that is true” in the mid-fourteenth century and accuracy or correctness in the mid-sixteenth century. In Old English it was triewð (ð is eth, a former letter for the th sound when it sounds like in the word “this”, making this word triewth) or treowð (treowth), where it meant faithfulness or being true. Not a big leap.
We can go into more depth when we look at the word true’s history. Triewð and treowð up there are both from the Old English word for faithful or trustworthy, triewe/treowe—the differences are due to the different dialects that made up Old English prior to the eleventh century, one being West Saxon (southern England, also the main dialect in the country) and the other Mercian (central England). It comes from the Proto Germanic trewwjaz, having good faith, and is thought to derive from the Proto Indo European dru, the word for tree (apparently the reason is because the idea is something like “steadfast as a tree”, but that’s all speculation).
Honestly, I’m just surprised Latin doesn’t play a part in this one. There’s not even any Greek, the other standby for the origins of English words. Although it’s, ahem, true that the classical Latin word for true, verus, did give us words like verify, very, veritable, and all the words they’re related to.
Tony Jebson’s page on the Origins of Old English