Webster's Revised Unabridged Dictionary · 1913

Grim

Grim (grim) , adjective

[Anglo-Saxon grim; akin to German grimm, equiv. to German & Dutch grimmig, Danish grim, grum, Swedish grym, Icelandic grimmr, German gram grief, as adj., hostile; compare Greek {not transcribed}, a crushing sound, {not transcribed} to neigh.]

Of forbidding or fear-inspiring aspect; fierce; stern; surly; cruel; frightful; horrible.
Whose grim aspect sets every joint a-shaking. — Shakespeare
The ridges of grim war. — Milton