The Collaborative International Dictionary of English v.0.48:

Cockle \Coc"kle\, n. [AS. coccel, cocel; cf. Gael. cogall tares,
   husks, cockle.] (Bot.)
   (a) A plant or weed that grows among grain; the corn rose
       (Luchnis Githage).
   (b) The Lotium, or darnel.
       [1913 Webster]