[Mithalwen]

Maybe as an extension of the hobbitish obsession with genealogies? I think Merry wrote at least a couple of books as well. Many people write without great hope,] or expectation that others will read them. Many diary keepers (including perhaps Tolkien himself who used code at times if I remember rightly) go to great lengths to ensure their diaries are kept private. Some go as far as to want them destroyed after their own deaths.