A corded fabric, originally made of silk, and worn by the kings of France in the chase. (French, cord du roy.)
Look well to your seat, 'tis like taking an airing On a corduroy road, and that out of repairing.
Lowell: Fable for Critics, stanza 2.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Corduroy from Infoplease: