Only some of us will remember the days when a car might have a rumble seat or – depending on which school you went to – a dicky seat, dickie seat or dickey seat.
Alf went to Wikipedia to jog his memory on the matter, and found a dicky seat described as
an upholstered exterior seat which hinges or otherwise opens out from the rear deck of a pre-World War II automobile, and seats one or more passengers.