The Collaborative International Dictionary of English v.0.48:

Algaroba \Al`ga*ro"ba\, n. [Sp. algarroba, fr. Ar. al-kharr?bah.
   Cf. Carob.] (Bot.)
   (a) The Carob, a leguminous tree of the Mediterranean region;
       also, its edible beans or pods, called St. John's
       bread.
   (b) The Honey mesquite (Prosopis juliflora), a small tree
       found from California to Buenos Ayres; also, its sweet,
       pulpy pods. A valuable gum, resembling gum arabic, is
       collected from the tree in Texas and Mexico.
       [1913 Webster] algaroth

The Collaborative International Dictionary of English v.0.48:

Carob \Car"ob\, n. [Cf. F. caroube fruit of the carob tree, Sp.
   garrobo, al-garrobo, carob tree, fr. Ar. kharr[=u]b, Per.
   Kharn[=u]b. Cf. Clgaroba.]
   1. (Bot.) An evergreen leguminous tree (Ceratania Siliqua)
      found in the countries bordering the Mediterranean; the
      St. John's bread; -- called also carob tree.
      [1913 Webster]

   2. One of the long, sweet, succulent, pods of the carob tree,
      which are used as food for animals and sometimes eaten by
      man; -- called also St. John's bread, carob bean, and
      algaroba bean.
      [1913 Webster]