The Collaborative International Dictionary of English v.0.48:

Shrag \Shrag\, n. [CF. Scrag.]
   A twig of a tree cut off. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shrag \Shrag\, v. t.
   To trim, as trees; to lop. [Obs.]
   [1913 Webster]