The Collaborative International Dictionary of English v.0.48:

Dado \Da"do\, n.; pl. Dadoes. [It. dado die, cube, pedestal;
   of the same origin as E. die, n. See Die, n.] (Arch.)
   (a) That part of a pedestal included between the base and the
       cornice (or surbase); the die. See Illust. of Column.
       Hence:
   (b) In any wall, that part of the basement included between
       the base and the base course. See Base course, under
       Base.
   (c) In interior decoration, the lower part of the wall of an
       apartment when adorned with moldings, or otherwise
       specially decorated. Daedal