Discord is certainly not a new word, but it's one of those that, if you look at it for too long or think about it too hard, starts to take on new forms.
We're used to seeing dis- as a prefix that makes a word the opposite of what follows it — like dishonesty, disloyalty, and disease. But if dis- is used that way in discord, where does that -cord come from?
Had the word discord been coined in the last forty years, one might conclude that it meant "to unplug; to disconnect a cord," as in "The printer doesn't have Bluetooth, so whenever I want to print something, I have to plug the printer into my laptop, send the job, and then discord the printer." (True story.)
Even if it didn't mean that — and it doesn't — I think we should start using it that way.
Of course, we've been dealing with cords long before computers came to being, so perhaps discord once meant "to untie," "to unload 128 cubic feet of firewood," or even "to sever the nervous tissue of the spine."
These are all just fanciful flights into etymological nonsense, one word-lover's sideways looks at a word and what it could mean. (It's fun. Try it sometime.)
Discord isn't even a verb. (Not usually, anyway.)
Discord isn't exactly like dishonesty, disloyalty, and disease. Although etymologically, the dis- prefix is the same for all four, the opposites of dishonesty, disloyalty, and disease (honesty, loyalty, and, if you think about it, ease) are arrived at simply by dropping the prefix.
But the opposite of discord isn't cord. It's accord. In that way, the antonymous pair is more like discredited and accredited. Dis- indicates "the opposite or absence of" and ac- (which also takes the forms ad-, af-, ag-, al-, ap-, as-, and at-, all of which are listed under the headword ad-) indicates "toward or to."
Which brings us back to -cord. Where does that come from?
If etymological flights of fancy like this tug at your heartstrings, you're probably nearer the answer than most: -cord comes from the Latin cors, meaning "heart."