It is called The People's Elbow because the elbow is a part of the body that goes under appreciated; without it your arms can't bend. It is a crucial function of the body. The song is talking about someone in love. It is talking about a girl and the singer will become her elbow. The elbow helps you do so many things and with love you can also do anything, all your dreams can come true and your life be made perfect.
Someday Came Suddenly, Attack Attack! - The People's Elbow