Strong’s Greek
G3684 — onikos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ὀνικός
onikos — pronounced on-ik-os'
from 3688; belonging to a ass, i.e. large (so as to be turned by a ass):--millstone. see GREEK for 3688
2 occurrences in the KJV.
Matthew 18:6
But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea.
Luke 17:2
It were better for him that a millstone were hanged about his neck, and he cast into the sea, than that he should offend one of these little ones.