Quiz: Remember the definition of mal de mer?
c.1825, "person in ragged clothing," from duds (q.v.). Sense extended by 1897 to "counterfeit thing," and 1908 to "useless, inefficient person or thing." This led naturally in World War I to "shell which fails to explode," and thence to "expensive failure."
c.1300, dudde "cloak, mantle," later in plural, "ragged clothing" (1560s), of uncertain origin.
: a dud bombnoun
Clothing; threads: To see them washed and put in and out of their duds was perhaps the greatest pleasure of her life
[1300+; origin unknown; perhaps fr one or another English or Celtic words meaning ''cloth, rag'']