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1738, as an anatomical term, from French cul-de-sac, literally "bottom of a sack," from Latin culus "bottom" (for second element, see sack (n.1)). Application to streets and alleys is from 1800.
cul-de-sac (kŭl'dĭ-sāk', kul'-)n. pl. culs-de-sac (kŭlz'-, kulz'-) or cul-de-sacs A saclike cavity or tube open only at one end.