Probably Silas is an abbreviation, like Lucas (Luke), Hermas, Amplias, Epaphras, Nymphas. etc. In Acts we find many such familiar names (cf. esp. Priscilla in Acts = Prisca Ro 16:3 RV, Sopater Ac 20:4 = Sosipater Ro 16:21). We might indeed have expected 'Silvas' not 'Silas,' but these abbreviations are very irregular. It has been suggested that Silas was the real name, and of Semitic origin, while Silvanus was adopted for a Roman name as being similar in sound; but then we should have expected for the latter 'Silanus,' not Silvanus.
Silas was a Christian prophet (Ac 15:32), one of the 'chief men among the brethren' (therefore doubtless of Jewish birth), who with 'Judas called Barsabbas' was sent as a delegate from the Apostolic Council with Paul and Barnabas, to convey the decision of the Council (Ac 15:22 ff.). He was also probably a Roman citizen (Ac 16:37), though this inference is denied by some. It is uncertain if he returned from Antioch to Jerusalem (Ac 15:34 is of doubtful authenticity), but in any case he was soon after chosen by Paul to go with him on the Second Journey, taking Barnabas' place, while Timothy afterwards took John Mark's. For this work Silas' double qualification as a leading Jewish Christian and a Roman citizen would eminently fit him. He accompanied Paul through S. Galatia to Troas, Philippi (where he was imprisoned), Thessalonica, and Ber