a heavy cotton pile fabric with lengthways ribs
The original form of this noun, in the late 18th century, was corderoy. The earliest use of the word that I could find is in The Manchester Mercury (Lancashire) of Tuesday 7th April 1772:
Manchester, March 23, 1772.
From a Bleaching Crest of Messrs Worsley and Worthington, at Garratt, on Saturday Night the 21st Instant.
One Piece of Half-ell Lin Corderoy three Races cut two uncut, about 32 Yards long, stamp’d with ER and other Marks; both Pieces dressed and half white.
It has often been assumed that corduroy represents a supposed French corde du roi, the king’s cord, as corduroy is a kind of ‘cord’ or corded fustian. But this is most probably a folk-etymological explanation of the later form of the English word, as no such name has ever been used in French. On the contrary, in Voyage dans les départemens du midi de la France (Journey in the departments of the South of France – 1807), among a list of articles manufactured at Sens, the French antiquary Aubin-Louis Millin de Grandmaison (1759-1818) enumerates
droguets, étoffes de coton, filatures, flanelles, futaines, kings-cordes.
druggets, cotton fabrics, spinnings [= yarns], flannels, fustians, ‘kings-cordes’.
The term kings-corde is evidently from English.
It has also been said that corduroy is from cord, ribbed fabric, and duroy, denoting a kind of lightweight worsted formerly made in the West of England. The word duroy, first recorded in the early 17th century, is of unknown origin. It might be from French du roi, of the king. The Glossaire to Encyclopédie Méthodique. Manufactures, arts et métiers (1790) contains the term duroi, denoting a woollen fabric similar to tammy.
But corduroy is unlikely to be a compound of cord and duroy, for several reasons. First, duroy denotes a woollen fabric while corduroy designates a cotton stuff, and these two words have apparently never been associated with each other. Secondly, grammatically, the compound would not be corduroy but duroy-cord. Lastly, this does not account for the earlier form, corderoy.
Another possible source has been pointed out in the English surname Corderoy, which in this case would be a maker’s name. This surname, also spelt Corderey, Cordurey, etc., was originally a nickname for a proud person: of French origin, it means king’s heart.
The British philologist Ernest Weekley (1865-1954) proposed the most convincing origin in Transactions of the Philological Society (1910):
Is there not a possibility that corduroy is folk-etymology for the common trade-term colour de roy?
The term colour de roy, which dates from the early 16th century, is from French couleur de roi, king’s colour. It originally denoted a cloth of a rich purple colour associated with the French kings and this colour itself. Later, it also signified a bright tawny colour and a cloth of this colour.
Ernest Weekley mentions that colour de roy occurs frequently in the scholarly editions of primary records of voyages, travels and other geographical material published by the Hakluyt Society. For example, in his diary, Richard Cocks (1566-1624), a merchant venturer living in Japan, wrote, on 26th November 1615:
The king sent for a bottell Spanish wyne, and desird to buy Mr. Osterwickes cloake, being of culler du roy, which he sent unto hym at price of 20 taies.
(Incidentally, Richard Cocks was one of the first known users of the expression Hobson’s choice.)
Ernest Weekley also cites Randle Cotgrave in A Dictionarie of the French and English Tongues (1611):
Couleur de Roy, was in old time, Purple; but now is the bright Tawnie, which wee also tearme, Colour de Roy.
And Weekley concludes:
The ‘bright tawnie’ is the commonest colour for new corduroys, and I imagine it might have been written commercially cᵒʳ de roy. This is, of course, a pure guess.