Named after Clapham's high street; 'Clapham' means the homestead or enclosure near a hill.
The Old English name was first recorded as Cloppaham around 880 and appears in the Domesday Book as Clopeham. The station opened in 1862 as Clapham and was also known as Clapham Road and Clapham Town. It got its present name in 1989 to avoid confusion with Clapham Junction.