The Collaborative International Dictionary of English v.0.48:

Attercop \At"ter*cop\, n. [AS. attercoppa a spider; [=ae]tter
   poison + coppa head, cup.]
   1. A spider. [Obs.]
      [1913 Webster]

   2. A peevish, ill-natured person. [North of Eng.]
      [1913 Webster]