double-decker

The term 'double-decker' is a transparent English compound, formed in the 19th century from the adjective 'double' and the agent noun 'decker'. 'Double' traces back to Latin duplus, meaning 'twofold', while 'deck' entered English from Middle Dutch dec (covering, roof), originally referring to a ship's platform. The suffix '-er' creates a noun indicating an object characterized by something, here the number of decks. The logic is perfectly literal: a 'double-decker' is an object, most famously a bus, characterized by having two decks or levels. Its application expanded from naval architecture to public transport and casual dining, always retaining its core sense of a two-tiered structure.

Structure: double (twofold) + decker (one that has decks) double: From Old French doble, from Latin duplus (twofold, double). In this compound, it functions as an adjective meaning 'having two'. decker: From the English noun deck (a platform or floor) + the agent suffix -er. It functions as a noun meaning 'one that has (a specified number of) decks'.