Source : Webster's Revised Unabridged Dictionary (1913)

Grewsome \Grew"some\, Gruesome \Grue"some\, a. [From a word akin
   to Dan. gru horror, terror + -some; cf. D. gruwzaam, G.
   grausam. Cf. {Grisly}.]
   Ugly; frightful.

         Grewsome sights of war.                  --C. Kingsley.