As far as St. Paul goes, here are some very interesting explantions by 2 of the greatest Christian minds ever.
St. Jerome says, *As Sergius Paulus Proconsul of Cyprus was the first to believe on hi**s preaching, he took his name from him because he had subdued him to faith in Christ… *[On Illustrious Men Chapter 5]
St. Augustine says,* Whence was Paul himself, who was first called Saul? That is, first proud, afterwards humble? For when he was Saul, his name was derived from Saul: now Saul was a proud king; and in his reign he persecuted the humble David) So when he who was afterwards Paul, was Saul, he was proud, at that time a persecutor of the innocent, at that time a waster of the Church. For he had received letters from the chief priests (burning as he was with zeal for the synagogue, and persecuting the Christian name), that he might show up whatever Christians he should find, to be punished. While he is on his way, while he is breathing out slaughter, while he is thirsting for blood, he is thrown to the ground by the voice of Christ from heaven the persecutor, he is raised up the preacher. In him was fulfilled that which is written in the Prophet, “I will wound and I will heal.” For that only in man cloth God wound, which lifteth itself up against God. He is no unkind physician who opens the swelling, who cuts, or cauterizes the corrupted part. He gives pain, it is true; but he only gives pain, that he may bring the patient on to health. He gives pain; but if he did not, he would do no good. Christ then by one word laid Saul low, and raised up Paul; that is, He laid low the proud, and raised up the humble. For what was the reason of his change of name, that whereas he was afore called Saul, he chose afterwards to be called Paul; but that he acknowledged in himself that the name of Saul when he was a persecutor, had been a name of pride? He chose therefore a humble name; to be called Paul, that is, the least. For Paul is, “the least.” Paul is nothing else but little. And now glorying in this name, and giving us a lesson of humility, he says, "I am the least of the Apostles.* [Sermon 27 Verse 2]