J.R.R. Tolkien studied Old English professionally as a philologist.
Old English, also called Anglo-Saxon, was the language used in England before the Norman Conquest and is preserved in works such as Beowulf. Tolkien’s scholarship included Old English language and literature, and his academic career included the Rawlinson and Bosworth Professorship of Anglo-Saxon at Oxford from 1925 to 1945.
Tolkien also knew and studied many other languages, including Welsh, Finnish, Latin, Greek, and Old Norse. This broad linguistic background influenced the sound and structure of his invented languages. Old English is especially relevant to names and language history in The Lord of the Rings, but it is not the same as Rohirric, the fictional language associated with Rohan. Tolkien used real historical languages as sources and inspirations rather than simply copying one language wholesale.