J.R.R. Tolkien’s academic specialty was philology.
Philology studies languages and texts, especially their historical development and relationships. Tolkien trained in English language and literature and became deeply interested in Old English, Middle English, Old Norse, Welsh, Finnish, and other languages. His professional work included teaching and researching the history of the English language.
His expertise strongly shaped his fiction. Tolkien often developed languages first or used the sound and structure of real languages as inspiration for fictional ones. The peoples, names, poems, and histories of Middle-earth were designed to feel as though they belonged to a deep linguistic past.
Philology is sometimes confused with linguistics, archaeology, or mythology. Those fields overlap with Tolkien’s interests, but philology best describes his academic discipline and professional identity. His famous 1936 lecture “Beowulf: The Monsters and the Critics” also demonstrated his influence on literary scholarship.