On page 398 Wolters writes:
After all, it would not be surprising if a person whom Paul numbers among his kinfolk (συγγενείς) should turn out to have a specifically Jewish name, comparable to the Μαρία of the previous verse.Not so fast! The problem here is that Μαρία is not a specifically Jewish name. As well as the Hebrew name, we have the Latin name, Maria, which is the feminine form of Marius. For this reason Tal Ilan writes,
of the 50 Mariams recorded, only 23 are indubitably Jewish. (Lexicon of Jewish Names in Late Antiquity Part III. p5)While the Maria of Rom 16:6 was almost certainly Jewish, it is likely that she kept her original name only because it also worked as a Roman name. When Palestinian Christian Jews travelled to Gentile territories where Semitic names would not have been familiar, they took a Greek or Latin name that would be recognized there. Cephas-Peter, Simeon-Simon, Saul-Paul, Silas-Silvanus, and John-Mark are good examples. It is hard to think of exceptions to this rule. Barnabas is a special case because the name carried significant meaning (Acts 4:36), which would have been lost if he had been given a familiar Greek or Latin name. Apart from Barnabas, Paul refers to no-one in Gentile territories by a Semitic name (Jesus called Justus of Col 4:11 is no exception because he probably never existed, and his Latin name is given in any case). So Wolter's suggestion that Paul referred to the hypothetical Yehunni by his Hebrew name has no good parallels. A man called Yehunni, after moving to Rome, would likely have taken a Greek or Latin name, such as Junius, rather than transliterating his name as Wolters supposes.
The likely original name of Junia is Joanna, since it is so similar in sound. Indeed Bauckham has argued that Junia was the Joanna of Luke 8:3; 24:10 (Gospel Women p109-202). Joanna was a common name in Palestine. Tal Ilan lists 12 women of that name in Palestine out of a total of 402 women (Lexicon of Jewish Names in Late Antiquity Part 1 Palestine 330 BCE-200 CE). Thus about 3% of women had that name. Wolters, on the other hand, finds only 2 men called Yehunni, which represents just 0.08% of the 2505 men listed by Tal Ilan. This figure of 0.08% for Yehunni is much less than the 3% for Joanna.
We can therefore be very confident that Junia was a woman.