The middle name in J.R.R. Tolkien’s full name is Reuel.
Tolkien’s full name was John Ronald Reuel Tolkien. The initials J.R.R. became his familiar literary name, but the third name is not a title or an invented name from Middle-earth. Reuel was used as part of his legal name and appears in biographical records.
His first name was John, while Ronald was the name used most often in his family and social life. The initials helped distinguish his authorial identity and became inseparable from the public image of the creator of The Hobbit and The Lord of the Rings.
Reuel is sometimes mistaken for one of Tolkien’s invented Elvish words because of its unusual sound. It is instead a personal name in Tolkien’s biography. The name also appears in family history through Tolkien’s father, Arthur Reuel Tolkien.