Had been a slave to Philemon of Colosse, and had run away from him, and fled to Rome; but being converted to Christianity through preaching of Paul, he was the occasion of Paul’s writing the epistle to Philemon, Colossians 4:9 Philemon 1:10.
These dictionary topics are from American Tract Society Bible Dictionary published in 1859. Public Domain, copy freely.
Rand, W. W. "Entry for 'ONESIMUS'". "American Tract Society Bible Dictionary".