 "Seychellum alluaudi" was first described in 1893 by Alphonse Milne-Edwards and Eugène Louis Bouvier, as a species in the genus "Deckenia", "D. alluaudi"; the specific epithet commemorates Charles A. Alluaud, who had collected the specimens they used.Unaware of that description, Mary J. Rathbun described ""Deckenia cristata"" in 1894, in a paper published in the "Proceedings of the United States National Museum"; her description was based on specimens donated to the United States National Museum by William Louis Abbott, who had travelled to the Seychelles in 1890.At the time, the only other species in the genus was "D. imitatrix" from the coast of East Africa, and a second species ("D. mitis"), also from East Africa, was added in 1898.