The Collaborative International Dictionary of English v.0.48:

Periwinkle \Per"i*win`kle\, n. [From AS. pinewincla a shellfish,
   in which pine- is fr. L. pina, pinna, a kind of mussel, akin
   to Gr. ?. Cf. Winkle.] (Zool.)
   Any small marine gastropod shell of the genus Littorina.
   The common European species (Littorina littorea), in Europe
   extensively used as food, has recently become naturalized
   abundantly on the American coast. See Littorina.
   [1913 Webster]

   Note: In America the name is often applied to several large
         univalves, as Fulgur carica, and Fulgur
         canaliculata.
         [1913 Webster]