1440, from M.Fr.
cordon "ribbon," dim. of O.Fr.
corde "cord" (see
cord). Sense of "a line of people or things guarding something" is 1758. Original sense preserved in
cordon bleu (1727) "the highest distinction," lit. "blue ribbon," for the sky-blue ribbon worn by the Knights-grand-cross of the Holy Ghost (highest order of chivalry); extended figuratively to other persons of distinction, especially, jocularly, to a first-rate cook.
Cordon sanitaire (1857), from Fr., a guarded line between infected and uninfected districts.
[kawr-dn] 
