Strong’s Greek
G1595 — hekousion
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἑκούσιος
hekousion — pronounced hek-oo'-see-on
neuter of a derivative from 1635; voluntariness:--willingly. see GREEK for 1635
1 occurrence in the KJV.
Philemon 1:14
But without thy mind would I do nothing; that thy benefit should not be as it were of necessity, but willingly.