Tolkien’s academic field at Oxford connected with Old and Middle English was philology.
Philology studies language through historical texts, including how words, sounds, and grammatical forms develop over time. Tolkien’s professional work centered particularly on Old English, Middle English, and related Germanic languages. His scholarship and teaching helped establish his reputation before and alongside his fame as a fantasy author.
He held the Rawlinson and Bosworth Professorship of Anglo-Saxon at Oxford from 1925 to 1945. He then became Merton Professor of English Language and Literature, a post he held until 1959. His academic interests included texts such as Beowulf and the Middle English poem Sir Gawain and the Green Knight.
Tolkien’s linguistic training strongly influenced his fiction. He invented languages with attention to historical change, sound patterns, and relationships between language communities. “Philology” is more precise here than “linguistics” in the modern broad sense, because Tolkien’s own academic identity and period vocabulary were rooted in historical language study.