The Collaborative International Dictionary of English v.0.48:

Marrowfat \Mar"row*fat\, n.
   A rich but late variety of pea.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rounceval \Roun"ce*val\, n.
   A giant; anything large; a kind of pea called also
   marrowfat. [Obs.]
   [1913 Webster]