The name 'Frognal' recalls a nook frequented by frogs.
Frognal is first recorded in the early 15th century as a customary tenement of the manor of Hampstead, probably on the site of the later Frognal House. The station opened in 1860 as Finchley Road St Johns Wood. Finchley Road is the turnpike to Finchley, completed in 1835.