Source : Webster's Revised Unabridged Dictionary (1913)

Worm \Worm\, v. i. [imp. & p. p. {Wormed}; p. pr. & vb. n.
   {Worming}.]
   To work slowly, gradually, and secretly.

         When debates and fretting jealousy Did worm and work
         within you more and more, Your color faded. --Herbert.