White Star Lines always denied that they ever intended to name her Gigantic. The one piece of evidence that might contradict that is a White Star publicity brochure, produced when the ships were first conceived, showing artist’s conceptions of the ships. In that brochure the third ship was labeled “Giganticâ€. Officially, Gigantic never existed.
Furthermore, the ship was not christened, launched, or registered under that name. Therefore, there could never have been an “RMS Giganticâ€.
Marty