The correct name is Isandlwana and not Isandhlwana. Rourke's Drift does not appear to be recorded as a place name See Annals of the Cape provincial Museums
Rorkes Drift was the spelling used on a British map created at the time September 1879
According to wikipedia it was called that because an Irishman called Rorke had had a trading post there.
Maps on this page uses the spelling Isandhwala but they are dated November 1879 (battle took place in January the article itself uses Isandlwana