The Collaborative International Dictionary of English v.0.48:

Shaddock \Shad"dock\, n. [Said to be so called from a Captain
   Shaddock, who first brought this fruit from the East Indies.]
   (Bot.)
   A tree (Citrus decumana) and its fruit, which is a large
   species of orange; -- called also forbidden fruit, and
   pompelmous.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pompelmous \Pom"pel*mous\, n.; pl. Pompelmouses. [D.
   pompelmoes; cf. G. pompelmuse, F. pamplemousse, and F.
   pompol['e]on.] (Bot.)
   A shaddock, esp. one of large size.
   [1913 Webster]