cul-de-sac (n.)

1738, as an anatomical term, "a diverticulum ending blindly," from French cul-de-sac, literally "bottom of a sack," from Latin culus "bottom, backside, fundament" (see tutu). For first element, see tutu; for second element, see sack (n.1). Application to a street or alley which has no outlet at one end is by 1819.