A corded fabric, originally made of silk, and worn by the kings
of France in the chase. (French, cord du roy.)
A term applied to roads in the backwoods and swampy districts of
the United States of America, formed of the halves of trees sawn in two
longitudinally, and laid transversely across the track. A road thus
made presents a ribbed appearance, like the cloth called corduroy.
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