mid-15c., "cord or ribbon worn as an ornament," from Middle French cordon "ribbon," diminutive of Old French 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," literally "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 French, a guarded line between infected and uninfected districts.
1560s, "to ornament with a ribbon;" 1891 as "to guard with a cordon;" from cordon (n.). Related: Cordoned; cordoning.