Named after the Knights of St John, who owned the woods here.
The manor of Lileston passed from the Knights Templar to the Knights of St John on the Templars' suppression in 1312; the order's English headquarters was Clerkenwell Priory. The knights' name passed to a wood in the manor, then to St John's Farm. Tube maps of 1938–39 show that the station, on the corner of Acacia Road, was to be called Acacia Road or Acacia.