Below, two shots of Tradescantia virginiana (or a hybrid) in Giverny, France. It's also in bloom right now in New York City.
Tradescantia is named for John Tradescant the Elder, a botanist from the early 17th Century; virginiana refers to the fact that this is a New World plant. As for the common name, I think I've mentioned before that when a common name ends with -wort, it is a clue that the plant has some homeopathic uses. Spiderwort, obviously enough, was used to cure spider bites (though I'm not sure it really works).
Tradescantia is in the Commeliniaceae family, and is related to the edible plant Commelina communis (or day-flower) . It's also related to a bedding plant called purple heart (Tradescantia pallida) and the popular indoor plant, Wandering Jew (Tradescantia zebrina).