It’s about time. We are now on Instagram!
Old English grindere "one who grinds (grain);" agent noun from grind (v.). Meaning "molar tooth" is late 14c. (Old English had grindetoð). Meaning "machine for milling" is from 1660s; of persons, from late 15c. Large sandwich sense is from 1954, though the exact signification is uncertain (perhaps from the amount of chewing required to eat one).