Easton's Bible Dictionary (1897)
Useful, a slave who, after robbing his master Philemon (q.v.) at Colosse, fled to Rome, where he was converted by the apostle Paul, who sent him back to his master with the epistle which bears his name. In it he beseeches Philemon to receive his slave as a “faithful and beloved brother.” Paul offers to pay to Philemon anything his slave had taken, and to bear the wrong he had done him. He was accompanied on his return by Tychicus, the bearer
of the Epistle to the Colossians (Philemon 1:16, 18). The story of this fugitive Colossian slave is a remarkable evidence of the freedom of access to the prisoner which was granted to all, and “a beautiful illustration both of the character of St. Paul and the transfiguring power and righteous principles of the gospel.”
Smith's Bible Dictionary (1863)
(profitable, useful), the name of the servant or slave in whose behalf Paul wrote the Epistle to Philemon. He was a native, or certainly an inhabitant, of Colosse. (Colossians 4:9) (A.D. 58.) He fled from his master end escaped to Rome, where he was led to embrace the gospel through Paul’s instrumentality. After his conversion the most happy and friendly relations sprung up between the teacher and disciple. Whether Paul desired his presence as
a personal attendant or as a minister of the gospel is not certain from verse 13 of the epistle.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
ONES'IMUS (useful), a slave of Philemon in whose behalf Paul wrote the Epistle to Philemon. Col 4:9. He seems to have fled from his master, Phile 15, but returned to him a Christian. His conversion was brought about through Paul at Rome. Phile 10. Tradition says he was afterward made bishop of Beraea, in Macedonia.
Hitchcock's Bible Names (1869)
profitable; useful