The overwhelming majority of Massiels on the web are the singer in question. According to Wikipedia, Massiel's real name is María de los Ángeles Santamaría Espinosa. Could it be she constructed it as a near-acronym? Goodle also uncovered an ancient and obscure anagrammatic reference of yours truly:
http://www.behindthename.com/bb/arcview.php?id=20812&board=gen http://www.behindthename.com/bb/arcview.php?id=20812&board=gen :)