Unknown; likely a literary invention
The name is most famously associated with the character Dejah Thoris from Edgar Rice Burroughs' Barsoom series. While its exact etymological roots are debated, it is often treated as a modern creative name in the United States. Some suggest a connection to the name Deja, meaning 'already' in French, but its literary usage predates that trend.
Princess of Mars and heroine of the Barsoom series · A Princess of Mars
American professional softball player
US births per 5-year period, 1990–present (SSA data).