St. Barnabas was a companion of St. Paul in the early apostolic ministry of the Church (cf. Acts 4:36-37; 9:26-27; 11:22-30; 12:25 – 15:40; I Cor. 9:6; Galatians 2). He was highly regarded for his preaching and the effectiveness of his witness, so his shield features an open Bible, presenting “the Gospel of our Lord Jesus Christ”, surrounded by three stones, recalling the manner of his martyrdom.
At Acts 4:36 the NKJV reads,
And Joses, who was also named Barnabas by the apostles (which is translated Son of Encouragement)
while the Living Bible (paraphrase) reads,
For instance , there was Joseph (the one the apostles nicknamed “Barny the Preacher”!)