J.R.R. Tolkien worked as a lexicographer on the Oxford English Dictionary project after World War I.
After leaving the army, Tolkien joined the staff working on what was then called the New English Dictionary, now known as the Oxford English Dictionary. He worked there from January 1919 until 1920, concentrating on words beginning with the letter W.
The job involved investigating word histories, meanings, spellings, and relationships across historical sources. Tolkien’s training in philology made him particularly suited to this work, and the experience gave him practical insight into how languages change over time.
Tolkien later became an academic and taught at the University of Leeds before joining the University of Oxford. His OED work is sometimes described simply as “working for the dictionary,” but lexicographer is the precise occupational term. It also helps explain why language history and word formation became central to both his scholarship and his invented languages.