The Collaborative International Dictionary of English v.0.48:

Kernel \Ker"nel\, n. [OE. kernel, kirnel, curnel, AS. cyrnel,
   fr. corn grain. See Corn, and cf. Kern to harden.]
   1. The essential part of a seed; all that is within the seed
      walls; the edible substance contained in the shell of a
      nut; hence, anything included in a shell, husk, or
      integument; as, the kernel of a nut. See Illust. of
      Endocarp.
      [1913 Webster]

            'A were as good crack a fusty nut with no kernel
                                                  --Shak.
      [1913 Webster]

   2. A single seed or grain; as, a kernel of corn.
      [1913 Webster]

   3. A small mass around which other matter is concreted; a
      nucleus; a concretion or hard lump in the flesh.
      [1913 Webster]

   4. The central, substantial or essential part of anything;
      the gist; the core; as, the kernel of an argument.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Kernel \Ker"nel\, v. i. [imp. & p. p. Kerneledor Kernelled;
   p. pr. & vb. n. Kerneling or Kernelling.]
   To harden or ripen into kernels; to produce kernels. Kerneled