'Hampstead' simply means homestead.
It comes from Anglo-Saxon ham and stede, a cognate of modern English 'homestead'; it appears in a grant of 986 by King Ethelred the Unready to St Peter's, Westminster. The station opened in the late 1870s as Loudoun Road, after its street, which takes its name from the Scottish landscape gardener John Claudius Loudon. It became South Hampstead in 1922.