The second of the 5 greeters in Philemon is here called simply "Mark", which was a very common Roman praenomen. About 16% of Roman citizens held the praenomen "Mark" (Marcus). The praenomen was reserved for use among relatives and close friends. A Roman would be referred to by his praenomen in the same context where a Greek's name would be abbreviated to a hypocoristic form. I showed here that Paul uses short name forms of those who send greetings in Philemon 23-24, and does so with good reason. So it comes as no surprise that we have a Latin praenomen in the list of greeters. It is therefore likely that this Mark was a Roman citizen, and that this was his praenomen. It is true that the name "Mark" could be used other than as a praenomen, but such cases account for only 0.14% of people recorded in the 6 volumes of the Lexicon of Greek Personal Names. While there are a disproportionate number of Paul's associates who seem to bare a Latin praenomen as their only name, it is unlikely that "Mark" was such a case.
In 2 Corinthians 8-9 Paul cites the example of the generosity of the Macedonians and makes it clear that they would learn whether the Corinthians lived up to their example. Paul uses similar tactics to encourage Philemon to send Onesimus back to him. He cites his own sacrifice (Philemon 9) and makes it clear that he expected to visit him (Philemon 22). Similarly he gives no fewer than 5 greeters, to show Philemon that all eyes are on him to see if he provides the requested benefaction. Epaphras is named first, presumably because his imprisonment provides the most powerful example of commitment for Philemon to emulate. Since Mark is included as a greeter, and is mentioned second, we should assume that he too exemplifies the type of behavior that Paul hopes Philemon will live up to. There is therefore every chance that this Mark was a benefactor of the church. Perhaps he was Aquila, who had given his house for the use of Paul and the church (Acts 18:2; 1 Cor 16:19; Rom 16:3-5). Notice that Aquila's name is mentioned before that of Prisca/Priscilla in the passages where his house is the focus (Acts 18:2 and 1 Cor 16:19), showing that he was the benefactor. It would be slightly surprising if Aquila were not mentioned in Philemon 23-24, since he was in the same city as Paul when Philemon was written (whether in Ephesus or Rome) and he and Prisca are mentioned first of those greeted in Rom 16.
So, "Mark" in Philemon 24 was almost certainly his praenomen. He is likely to have been a benefactor such as Aquila.
The author of Colossians, though, seems to equate this Mark with John-Mark (Col 4:10). This is historically unlikely since Paul and Mark had split up before Colossians could have been written (Acts 15:37-39). Also, John Mark did not exemplify the commitment that Paul wanted to provide as an example for Philemon. Quite the reverse (Acts 13:13). The author of Colossians seems to have made the natural mistake of equating the Mark of Philemon 24 with the famous man of the same name.
The name Demas is an abbreviation of the name Demetrius. Of the 300,584 entries in the 6 volumes of the Lexicon of Greek Personal Names, only 26 are called Demas, but 2547 are called Demetrius. This further illustrates that Paul is using informal names for the greeters in Philemon. Demas would ordinarily have been referred to by his full name, "Demetrius".
In my next post I will suggest why Paul does not abbreviate the name "Aristarchus", and speculate on his identity. Any guesses?