Old English grimm "fierce, cruel, savage; severe, dire, painful," from Proto-Germanic *grimma- (source also of Old Saxon, Old Frisian, Old High German, German grimm "grim, angry, fierce," Old Norse grimmr "stern, horrible, dire," Swedish grym "fierce, furious"), from PIE *ghremno- "angry," which is perhaps imitative of the sound of rumbling thunder (compare Greek khremizein "to neigh," Old Church Slavonic vuzgrimeti "to thunder," Russian gremet' "thunder").
A weaker word now than it once was; sense of "dreary, gloomy" first recorded late 12c. It also had a verb form in Old English, grimman (class III strong verb; past tense gramm, past participle grummen), and a noun, grima "goblin, specter," perhaps also a proper name or attribute-name of a god, hence its appearance as an element in place names.
Grim reaper as a figurative phrase for "death" is attested by 1847 (the association of grim and death goes back at least to 17c.). A Middle English expression for "have recourse to harsh measures" was to wend the grim tooth (early 13c.).
"organized massacre in Russia against a particular class or people, especially the Jews," 1882, from Yiddish pogrom, from Russian pogromu "devastation, destruction," from po- "by, through, behind, after" (cognate with Latin post-; see post-) + gromu "thunder, roar," from PIE imitative root *ghrem- (see grim).
1580s, "complain in a low voice;" 1590s, "make a low, rumbling sound," from French grommeler "mutter between the teeth" or directly from Middle Dutch grommelen "murmur, mutter, grunt," from grommen "to rumble, growl." Imitative, or perhaps akin to grim (adj.). With unetymological -b- as in mumble. Related: Grumbled; grumbling.
1580s, of uncertain origin, probably alteration of Middle English grim "dirt, filth" (early 14c.), from Middle Low German greme "dirt" or another Low German source, from Proto-Germanic *grim- "to smear" (source also of Flemish grijm, Middle Dutch grime "soot, mask"), from PIE root *ghrei- "to rub." The verb was Middle English grymen (mid-15c.) but largely was replaced early 16c. by begrime.
"female monster with a petrifying look," late 14c., in Greek legend, any of the three hideous sisters, with writhing serpents for hair, whose look turned beholders to stone, from Greek Gorgones (plural; singular Gorgō) "the grim ones," from gorgos, of a look or gaze, "grim, fierce, terrible," later also "vigorous, lively," a word of unknown origin. Beekes' sources reject the proposed connections to Old Irish garg "raw, wild," Old Church Slavonic groza "shiver," Armenian karcr "hard."
Transferred sense of "terrifyingly ugly person" is from 1520s. Their names were Medusa, Euryale, and Stheino, but when only one is mentioned, Medusa usually is meant. Slain by Perseus, her head was fixed on the aegis of Athena.
