The Stranger and Meursault

Who is this "stranger"? Is this referring to Meursault, or is there another connection within this book? I think that the title of this book is named after the metaphor of who Meursault is to other people, and to himself as well. No one truly knows who Meursault is. He is a mystery. Not even Meursault knows   who the true Meursault is. People spend time with him and they think they know him, but no one does. One who does not know them self cannot be acknowledged by others. I think the title of the book comes from this lack of character in Meursault, because he is simply a stranger to everybody.