Forklore: Beet it!
We call it Swiss chard, but the English call it silverbeet, and the English are right. Botanically, chard is a beet-- Beta vulgaris cicla. In fact, it is pretty close to the original beet, the variety that was first cultivated in ancient Mesopotamia.
The Arabic name of the plant, al-silq, reached Spain as acelga. At one time scholars thought the name al-silq showed that chard originally came from Sicily, but we now know that it goes back to a Babylonian word, silqu. It's no more Sicilian than it is, well, Swiss.
The Romans, who called chard beta, cultivated it for its leaves, just like the Babylonians and everybody else. Its roots were small and the Romans considered them basically of medicinal value.
It wasn't until around the 17th Century that the modern beet with large red roots was developed. The root's flavor is actually rather close to chard--compare a just-cooked beet with a chard leaf and you'll note the same fresh, earthy aroma--but it was much sweeter (if less nutritious) and became an instant success.
It was so successful that it totally usurped the name beet in this country. The English, at least, are still careful to say beet root when they mean the red kind.