J.R.R. Tolkien’s first name was John, making his full name John Ronald Reuel Tolkien.
The author was generally known within his family as Ronald, or sometimes Ronald Tolkien, rather than by his first given name. His initials therefore represent John, Ronald, and Reuel. “Reuel” was a family name with connections to Tolkien’s ancestry and was not the name of a fictional character.
Tolkien used the initials J.R.R. Tolkien on his books, and that form became internationally familiar. The initials distinguish him from his son Christopher Tolkien, who later edited and published many works from his father’s papers. Tolkien’s signature and scholarly publications also commonly used the initialed form.
Names are especially significant in Tolkien’s fiction because languages and naming systems are central to his world-building. However, the three initials in his author name are biographical rather than invented Middle-earth terms. The most direct expansion is John Ronald Reuel Tolkien.