What language did J.R.R. Tolkien teach at Oxford University from 1925?

J.R.R. Tolkien taught Anglo-Saxon at Oxford University from 1925.

The formal academic name for the subject was Old English, also called Anglo-Saxon. Tolkien held the Rawlinson and Bosworth Professorship of Anglo-Saxon at Pembroke College, Oxford, from 1925 until 1945. His work involved the language and literature of early medieval England.

Tolkien was not only a novelist. He was a philologist, a scholar who studies languages and their historical development. His professional knowledge of Old English, Old Norse, Welsh, Finnish, and other languages strongly influenced the sounds and structures of his invented languages. A common mix-up is confusing Anglo-Saxon with Middle English: Old English was spoken before the Norman Conquest, while Middle English developed later. Tolkien subsequently became Professor of English Language and Literature at Oxford’s Merton College.