It's named after the Sultan of Selangor at the time of its construction in the late 1890s.
Apart from the name though, this structure took its influences from much further afield, mostly from the hybrid architectural style known as Indo-Saracenic.
Most of the structure is not open to the public, which is a shame, as its former administrative and judicial functions have for the most part been moved elsewhere.
For the time being, the best way to get a sense of the Sultan Abdul Samad Building is from Merdeka Square. It looks particularly attractive at night, when it is lit up in a range of colours.