"large, clumsy type of tropical fish, sunfish," 1670s, from Latin mola, literally "millstone" (from PIE root *mele- "to crush, grind"). So called because of the fish's shape and rough skin. Attested in nativized form mole from c. 1600.
also mole (late 14c.), "false conception; shapeless, compacy, fleshy mass in the uterus," from Latin mola "false conception," from earlier sense "salt cake;" literally "millstone" (from PIE root *mele- "to crush, grind"). The Latin form is attested in English from c. 1600.
*melə-, Proto-Indo-European root meaning "to crush, grind," with derivatives referring to ground or crumbling substances and crushing or grinding instruments.
It forms all or part of: amyl; amyloid; blintz; emmer; emolument; immolate; maelstrom; mall; malleable; malleolus; mallet; malleus; maul; meal (n.2) "edible ground grain;" mill (n.1) "building fitted to grind grain;" millet; mola; molar (n.); mold (n.3) "loose earth;" molder; ormolu; pall-mall.
It is the hypothetical source of/evidence for its existence is provided by: Hittite mallanzi "they grind;" Armenian malem "I crush, bruise;" Greek mylos "millstone," myle "mill;" Latin molere "to grind," mola "millstone, mill," milium "millet;" Old English melu "meal, flour;" Albanian miel "meal, flour;" Old Church Slavonic meljo, Lithuanian malu, malti "to grind;" Old Church Slavonic mlatu, Russian molotu "hammer."
"grinding tooth, back-tooth," mid-14c., from Latin molaris dens "grinding tooth," from mola "millstone," from PIE root *mele- "to crush, grind." As an adjective, "grinding, crushing," as distinguished from "cutting" or "piercing," from 1620s. In Old English they were cweornteð "quern-teeth."
"uncrystallized syrup produced in the manufacture of sugar," 1580s, from Portuguese melaço, from Late Latin mellaceum "new wine," properly neuter of mellaceus "resembling honey," from Latin mel (genitive mellis) "honey" (from PIE root *melit- "honey"). Adopted in English in plural form and generally remaining so, but regarded as a singular noun.
Middle English mille, "building fitted to grind grain," Old English mylen "a mill" (10c.), an early Germanic borrowing from Late Latin molina, molinum "mill" (source of French moulin, Spanish molino), originally fem. and neuter of molinus "pertaining to a mill," from Latin mola "mill, millstone," related to molere "to grind," from PIE root *mele- "to crush, grind." The -n- gradually was lost in English but survives in the surname Milner. Also from Late Latin molina, directly or indirectly, are German Mühle, Old Saxon mulin, Old Norse mylna, Danish mølle, Old Church Slavonic mulinu.
The meaning "mechanical device for grinding grain for food" is from 1550s. The broader sense of "machine for grinding or pulverizing any solid substance" is attested from 1670s. Other types of manufacturing machines driven by wind or water, that transform raw material by a process other than grinding began to be called mills by early 15c. Sense of "large building fitted with industrial machinery for manufacturing" is from c. 1500. In old slang also "a typewriter" (1913); "a boxing match or other pugilistic bout" (1819).