The term 'Double-Decker Bus' refers to a type of bus that has two levels, with the upper level typically used for seating and the lower level used for luggage or cargo. This type of bus is popular in many cities around the world, as it allows for more passengers to be transported at once. The term 'Double-Decker Bus' is derived from the 6-letter word 'Decker, ' which is an old English term meaning 'two stories.'