Word Origin & History
dud
1307, dudde "cloak, mantle," later duds "ragged clothing" (1508), of uncertain origin. Extended c.1825 to "person in ragged clothing," in 1897 to "counterfeit thing," and 1908 to "useless, inefficient person or thing." This led naturally in WWI to "shell which fails to explode," and thence to "expensive failure."