What was J.R.R. Tolkien’s professional specialty while working on the Oxford English Dictionary?

J.R.R. Tolkien worked on the Oxford English Dictionary as a specialist in Germanic philology.

From 1919 to 1920, Tolkien worked on the dictionary’s staff after returning from military service and completing his degree at Oxford. His work focused especially on words beginning with the letter W, including their histories, forms, and relationships across Germanic languages.

Philology was the historical study of language through texts, sound changes, grammar, and word origins. Tolkien’s expertise in Old English, Middle English, Old Norse, Gothic, Welsh, and other languages supported both his academic work and his invented languages.

The dictionary job is often simplified into the claim that Tolkien wrote the Oxford English Dictionary. He did not compile the whole dictionary; he contributed research and definitions as one member of a much larger editorial project. His experience helped strengthen his understanding of how words evolve and how related languages reveal older forms.