The Greek word allóphylos (ἀλλόφυλος) combines allos (other) and phyle (tribe/race). It means one of a different tribe or race, translated in the LXX (Septuagint) as 'Philistine' and in the New Testament as 'foreigner.'
In the LXX, allóphylos consistently translates 'Philistine,' making it the Greek word for Israel's ancient nemesis. In Acts 10:28, Peter uses it to describe the barrier between Jews and Gentiles that Christ has broken down: 'You are well aware that it is against our law for a Jew to associate with or visit a foreigner (allóphylos).' What was once the word for the enemy — the uncircumcised Philistine — becomes in Peter's mouth the description of those whom God has now included in His family. The gospel demolishes the walls that separate tribes and races.