Source : Webster's Revised Unabridged Dictionary (1913)

Case \Case\ (k[=a]s), n. [OF. casse, F. caisse (cf. It. cassa),
   fr. L. capsa chest, box, case, fr. capere to take, hold. See
   {Capacious}, and cf. 4th {Chase}, {Cash}, {Enchase}, 3d
   {Sash}.]
   1. A box, sheath, or covering; as, a case for holding goods;
      a case for spectacles; the case of a watch; the case
      (capsule) of a cartridge; a case (cover) for a book.

   2. A box and its contents; the quantity contained in a box;
      as, a case of goods; a case of instruments.

   3. (Print.) A shallow tray divided into compartments or
      ``boxes'' for holding type.

   Note: Cases for type are usually arranged in sets of two,
         called respectively the upper and the lower case. The
         {upper case} contains capitals, small capitals,
         accented and marked letters, fractions, and marks of
         reference: the {lower case} contains the small letters,
         figures, marks of punctuation, quadrats, and spaces.

   4. An inclosing frame; a casing; as, a door case; a window
      case.

   5. (Mining) A small fissure which admits water to the
      workings. --Knight.

Source : WordNet®

lower case
     n : the characters that were once kept in bottom half of a
         compositor's type case [syn: {small letter}, {lower-case
         letter}, {minuscule}] [ant: {capital}]