The Collaborative International Dictionary of English v.0.48:

Water chinquapin \Wa"ter chin"qua*pin\ (Bot.)
   The American lotus, and its edible seeds, which somewhat
   resemble chinquapins. Cf. Yoncopin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

water chinquapin
    n 1: water lily of eastern North America having pale yellow
         blossoms and edible globular nutlike seeds [syn: water
         chinquapin, American lotus, yanquapin, Nelumbo
         lutea]
    2: edible nutlike seeds of an American lotus having the flavor
       of a chinquapin