"grinding tooth," mid-14c., from Latin molaris dens "grinding tooth," from mola "millstone," from PIE root *mel- "to rub, grind" (see mill, n.1). As an adjective in this sense from 1620s. In Old English they were cweornteð "quern-teeth."

in chemistry, "pertaining to one mole," 1902, from mole(4) + -ar.