“Captain Nemo” is a pseudonym, the name by which the captain of the Nautilus introduces himself to Professor Arronax, Consiel, and Ned Land. As the captain admits to Arronax’s inquiry, the crew of the Nautilus speaks a language developed by the captain himself, therefore we may conclude that the captain has chosen the word “nemo”, which means “no man” or “no one” in Latin, as a symbolic name.
In Jules Verne’s later novel, Mysterious Island, Captain Nemo befriends the stranded crew of a Civil War hot-air balloon, and shows them what became of the Nautilus.