Heidegger's Bible Handbook: 1 Thessalonians: Inscription
1. The Inscription of the Epistle. Thessalonica, a city of Macedonia. At first called Halia, and Therma. The entrance of Saint Paul into that city, with the Jews setting themselves in opposition to him, and with Timothy sent by the same, so that he might confirm them.
The Epistle is inscribed τῇ Ἐκκλησίᾳ Θεσσαλονικέων, to the Church of the Thessalonians. Now, Thessalonica was a city of Macedonia, μάλιστα τῶν ἄλλων εὐανδροῦσα, abounding more than other cities in the strength and valor of citizens, as Strabo says, Geography VII. At first it was called Halia and Therma. Saint Paul came into that city, and found a Synagogue of the Jews, entering which, He taught that it was necessary for the Christ to suffer, and to rise from the dead. Upon which some, having been converted, προσεκληρώθησαν/ consorted with Paul and Silas. But other Jews, moved with immoderate zeal, stirred up such commotions, that Paul and Silas, sent away by night, betook themselves to Berea. Where, while they were found to be εὐγενέστεροι, more noble, than the Thessalonians had been, and were giving their assent to Paul, disturbers from Thessalonica did not hesitate to agitate there also, to such an extent that Paul found it necessary to betake himself to Athens, with Silas and Timothy remaining in Berea. These things are found in Acts 17:1-13. Afterwards the Apostle at Athens sent Timothy to the Thessalonians, so that he might confirm the believers found there, and comfort them, τῷ μηδένα σαίνεσθαι ἐν ταῖς θλίψεσι ταύταις, that is, that no man should be moved by these afflictions, since they themselves knew that they were appointed thereunto, 1 Thessalonians 3:1-3.