Saul to Paul

[Acts 13:9] Then Saul, (who also is called Paul,) filled with the Holy Ghost, set his eyes on him,
The history concerning Paul's parents is meager; in fact, nothing is known of his mother, and all that is known of his father is that he was a Pharisee (Acts 23:5), and from his father Paul inherited the rights of Roman citizenship (Acts 22:26). Although the exact date of Paul's birth is unknown, ancient tradition places it the second year after Messiah's birth.
According to Jewish tradition Paul, like all boys, had to learn a trade, his was tent making. Following this, at the proper age, perhaps about thirteen, he went to Jerusalem to pursue his studies of the Jews. He became a student of Gamaliel, a distinguished teacher of the Law (Acts 22:3), and he was greatly interested in Mosaic Law. Through his study Saul grew increasingly more familiar with the outward observance of the law,
Then Saul, (who also is called Paul) - This is the last time he is called Saul. Henceforward he is designated by the title by which he is usually known, as Paul. When, or why, this change occurred in the name, has been a subject on which commentators are not agreed. From the fact that the change in the name is here first intimated, it would seem probable that it was first used in relation to him at this time. By whom the name was given him--whether he assumed it himself, or whether it was first given him by Christians or by Romans-- is not intimated. The name is of Roman origin. In the Latin language the name Paulus signifies little, dwarfish; it was assumed or conferred in subsequent years because he was little in stature. The name is not of the same signification as the name Saul. This signifies one that is asked, or desired.
After all the conjectures on this subject, it is probable:
1. That this name was first used here; for before this, even after his conversion, he is uniformly called Saul.
2. That it was given by the Romans, as being a name with which they were more familiar, and one that was more consonant with their language and pronunciation. It was made by the change of a single letter; and probably because the name Paul was common among them, and pronounced perhaps with greater facility. The reason for the selection of Paul is that it comes from the Greek Paulos, meaning little, and when converting to Christianity Paul wished to be known as the "Little One".
3. Paul suffered himself to be called by this name, as he was employed chiefly among the Gentiles. It was common for names to undergo changes quite as great as this, without our being able to specify any particular cause, in passing from one language to another.
4. G-d did change Peter's name, and many people assume that Paul's name was also changed, but it wasn't. Paul just changed the people he associated with and the language that he used. Paul's ministry was to the Gentiles, and he may have begun using Paul more because of that, but he already had that name as a citizen of Rome.
5. Saul was described as a man around thirty years of age when Stephen was killed and the Jews remembered ‘Saul as the persecutor!’ He made havoc for the Messianic Church invading sanctuaries of domestic life, entering every house (Acts 8:3) and tearing people from their homes and committing them to prison. Not only did he make men suffer, also, a fact three times repeated as a great aggravation of his cruelty (Acts 8:3). The persecuted people were scourged in their own Synagogues (Acts 26:11). He later confessed, "I persecuted this way unto death, binding and delivering into prisons both men and women (Acts 22:4), and when they were put to death I gave my voice against them" (Acts 26:10). He even tried causing them to blaspheme (Acts 26:11). His fame as a notorious inquisitor was known far and wide.
6. Paul, was a native of Tarsus, a city of Cilicia (Acts 21:39; 22:3), was of Jewish descent from the tribe of Benjamin (Philippians 3:5) and had knowledge of Greek. According to Ramsey (Paul the Traveler, p. 81) "it was the fashion for every Syrian, Cilician, and Cappadocian who prided himself on his Greek education and his knowledge of the Greek language to bear a Greek name; but at the same time he had his other name by which he was known unfavorably by his countrymen in general.