Other forms: grinding, grinds
The grind is dull hard work that never lets up. The same thing, every day, with no end in sight.
The noun is informal and weary, and the daily grind is close to a fixed phrase. There is a separate and much older verb meaning to crush into powder, so grinding coffee or grinding corn is the literal sense that all of this comes from. Grinding to a halt describes a slow unwilling stop, and grinding your teeth is what you do in your sleep.
Proto-Germanic
*grindaną — to crush, grind
Proto-West Germanic
*grindan
Old English
grindan — to grind
Middle English
grynden
English, today
grind
From Middle English grynden, from Old English grindan (“to grind”), from Proto-West Germanic grindan, from Proto-Germanic grindaną (“to crush, grind”). Cognate with stq gríende, griene (“to grind, mill”), West Frisian grintsje (“to crush, punish”), Dutch grinden (“to grind”) and grind (“gravel, shingle”), Albanian grind (“to brawl, fight”).
Etymology from Wiktionary, CC BY-SA