The Collaborative International Dictionary of English v.0.48:

Cranberry \Cran"ber*ry\ (kr[a^]n"b[e^]r*r[y^]), n.; pl.
   Cranberries (-r[i^]z). [So named from its fruit being ripe
   in the spring when the cranes return. --Dr. Prior.] (Bot.)
   A red, acid berry, much used for making sauce, etc.; also,
   the plant producing it (several species of Vaccinum or
   Oxycoccus.) The high cranberry or cranberry tree is a
   species of Viburnum (Viburnum Opulus), and the other is
   sometimes called low cranberry or marsh cranberry to
   distinguish it.
   [1913 Webster] cranberry tree