Saint Onesimus was a slave to Philemon of Colossae, a man of Christian faith. His name means "useful."
If this Saint's name sounds familiar, there's a reason for that. The apostle Paul wrote the Epistle to Philemon to the slave-master Philemon concerning a runaway slave called Onesimus, whose name means "useful." This slave found his way to the site of Paul's imprisonment (most probably Rome or Caesarea) to escape punishment for a theft of which he was accused. After hearing the Gospel from Paul, Onesimus converted to Christianity.
Learn more about St. Onesimus in this video by Catholic Priest.