LotR -- Book 1 - Chapter 01 - A Long-Expected Party

[Mister Underhill]

Originally Posted by The Saucepan Man

But the reference is still to my mind incongruous with the fiction of the story having been written by the Hobbits.

On the other hand, you can chalk it up as a liberty taken by the "translator" of the Red Book (i.e., Tolkien), just as the word "Hobbit" itself is an invention, and other Hobbit family and place names have been normalized for the modern reader. See the very last page in RotK, at the end of the appendices.

By casting himself in the rôle of translator, Tolkien is able to smooth over any straggling errors, anachronisms, or inconsistencies in his work. A stroke of genius on his part, I'd say.