Emily Dickinson Lexicon

GRIM, a. [Sax. grim, fierce, rough, ferocious; gram, raging fury; gremian, to provoke; D. gram, angry; grimmen, to growl; grimmig, grim; grommen, to grumble; G. grimm, furious, grim; grimmen, to rage; gram, grief, sorrow; Dan. grim, stern, grim, peevish; gram, grudging, hating, peevish; W. gremiaw, to gnash, to snarl, from rhem, whence rhemial, to mutter. Hence Fr. grimace. These words belong probably to the root of L. fremo, which has a different prefix, Gr. βρεμω, Eng. grumble, rumble, Ir. grim, war. See Class Rm, No. 11, 13.]

1. Fierce; ferocious; impressing terror; frightful; horrible as, a grim look; a grim face; grim war. Milton. Addison
2. Ugly; ill-looking. Shak.
3. Sour; crabbed; peevish; surly.