Strong's:ὀνικός belonging to a ass, i.e. large (so as to be turned by a ass)Derivation: from G3688;KJV Usage: millstone. G3688
TBESG:ὀνικόςhuge millstoneG:A ὀνικός, -ή, -όν (< ὄνος), of or for an ass. μύλος ὀ., Refs Mat.18:6, Mrk.9:42 (elsewhere only in π.; see MM, xviii).† (AS)
ὀνικός onikos on-ik-os' From G3688; belonging to an ass, that is, large (so as to be turned by an ass)KJV Usage: millstone.
ὀνάριον onarion on-ar'-ee-on Neuter of a presumed derivative of G3688; a little assKJV Usage: young ass.