grinder n.

Old English grindan "to rub together, crush into powder, grate, scrape," forgrindan "destroy by crushing" (class III strong verb; past tense grand, past participle grunden), from Proto-Germanic *grindanan (source also of Dutch grenden), related to ground (v.), from PIE *ghrendh- "to grind" (source also of Latin frendere "to gnash the teeth," Greek khondros "corn, grain," Lithuanian grendu, gręsti "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 (compare Dutch malen, Old Norse mala, German mahlen).

1955, the New York City term for a sandwich elsewhere called submarine, grinder, poor boy (New Orleans), or hoagie (Philadelphia); origin unknown, perhaps so called for its great size (from hero (n.1)), or a folk-etymology alteration of Greek gyro as a type of sandwich.