Molar, from the Latin mola, mill or millstone. The upper and lower molars, grinding as we chew, work like millstones.

Mola also gave us immolate, to kill or destroy. The original meaning of immolate was sacrificial killing; its derivation stems from the ancient custom of sprinkling victims with salted, ground grain.

One example of an ancient Roman mola. Donkeys (or slaves) would push the handles to turn the millstone and grind the grain, poured in at the top, against the circular stone base. The device pictured is about 5 feet high. Drawing from www.dl.ket.org/latin2/mores/slaves/countryslave.htm

Upper and lower first molars. Notice the matching contours of the crowns' surfaces, an adaptation for grinding action. Adpated from dentistry.uic.edu/depts/oralb/OCCREVIS.htm