What was the title of J.R.R. Tolkien's first published scholarly work?

J.R.R. Tolkien's first published scholarly work was titled The Devil's Coach Horses.

The essay appeared in 1925 in the journal English Studies. It examined the expression “devil's coach horses,” a historical term connected with certain beetles, and demonstrated Tolkien's interest in the origins and development of words.

This early publication came before many of Tolkien's most famous academic essays and before his major works of fiction reached the public. His scholarly career was already developing through research and teaching in Old and Middle English, Germanic philology, and medieval literature.

The title is sometimes confused with The Monsters and the Critics, Tolkien's influential 1936 lecture and essay about Beowulf, or with On Fairy-Stories, his important discussion of fantasy and fairy tales. Those works are better known, but neither was his first published scholarly work. Bibliographies also contain many later editions and collections, so publication chronology matters when identifying this early essay.