The Collaborative International Dictionary of English v.0.48:

Rob \Rob\, n. [F.; cf. Sp. rob, It. rob, robbo, Pg. robe,
   arrobe, Ar. rubb, robb, Per. rub.]
   The inspissated juice of ripe fruit, obtained by evaporation
   of the juice over a fire till it acquires the consistence of
   a sirup. It is sometimes mixed with honey or sugar. [Written
   also rhob, and rohob.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rhob \Rhob\ (r[o^]b), n.
   See 1st Rob.
   [1913 Webster]