"Helen" is about the most famous of Helen of all time. No, not Helen Keller, not Helen Mirren, but Helen of Troy.
Legend has it that Helen of Troy was the most beautiful woman of all time, and that this very beauty was the catalyst of a ten-year war between Greece and Troy. That's a whole lot of burden to put on one lady's (beautiful) shoulders, if you ask us. If you want to know more about Helen, check out what we've got to say about her over in the "In a Nutshell" section, or in our mythology learning guide.
H.D.'s short poem is all Helen, all the time, so the title is pretty fitting in our humble opinion. And it's also in keeping with H.D.'s habit of keeping her titles short and sweet, like "Oread" and "Sea Rose."