Why is the ninth month called September?
Old English grund "bottom, foundation, ground, surface of the earth," especially "bottom of the sea" (a sense preserved in run aground), from Proto-Germanic *grundus, which seems to have meant "deep place" (cf. Old Frisian, Old Saxon, Danish, Swedish grund, Dutch grond, Old High German grunt, German Grund "ground, soil, bottom;" Old Norse grunn "a shallow place," grund "field, plain," grunnr "bottom"). No known cognates outside Germanic. Sense of "reason, motive" first attested c.1200; electrical sense is from 1870.
mid-13c., "to put on the ground, to strike down to the ground," from ground (n.). Of ships, "to run into the ground," from mid-15c. Meaning "to base" (an argument, sermon, etc.) is late 14c. Meaning "deny privileges" is 1940s, originally a punishment meted out to pilots (in which sense it is attested from 1930). Related: Grounded; grounding.
"reduced to fine particles by grinding," 1765, past participle adjective from grind.
Old English grindan "to rub together, grate, scrape," forgrindan "destroy by crushing" (class III strong verb; past tense grand, past participle grunden), from Proto-Germanic *grindanan (cf. Dutch grenden), related to ground, from PIE *ghrendh- "to grind" (cf. Latin frendere "to gnash the teeth," Greek khondros "corn, grain," Lithuanian grendu "to scrape, scratch"). Meaning "to make smooth or sharp by friction" is from c.1300. Most other Germanic languages use a verb cognate with Latin molere (cf. Dutch malen, Old Norse mala, German mahlen).
late 12c., "gnashing the teeth," from grind (v.). The sense "steady, hard work" first recorded 1851 in college student slang (but cf. gerund-grinder, 1710); the meaning "hard-working student" is American English slang from 1864.
bump and grind, if you can't find 'em
(Ex. 32:20; Deut. 9:21; Judg. 16:21), to crush small (Heb. tahan); to oppress the poor (Isa. 3:5). The hand-mill was early used by the Hebrews (Num. 11:8). It consisted of two stones, the upper (Deut. 24:6; 2 Sam. 11:21) being movable and slightly concave, the lower being stationary. The grinders mentioned Eccl. 12:3 are the teeth. (See MILL.)