"my true companion"

Philippians 4:1-3

Paul uses some pretty extreme language to describe how much he loves the church at Philippi: my joy, my crown, dear friends, those whom I love and long for. It's obvious that this church holds a very special place in his heart. That's why it must grieve him so much that Euodia (is that the Greek form of Yoda?) and Syntyche were causing divisions.
Paul gives three instructions: stand firm, be of the same mind in the Lord (Euodia and Syntyche especially), and to help these two women reach unity in mind. Unity was hugely important to Paul, possibly because any disunity would provide a crack for Satan to pick at to destroy a church and people's faith and possibly because, according to Ephesians, unity displays the wisdom of God to the spiritual forces in the heavenly realms.
These instructions could be given today: stand firm - don't give up, don't give in, don't stray from the truth and keep striving after righteousness and sanctification. I think that because we are a fast-food society, we're not willing to put much effort into anything - if we don't see instant results, we give up and move on. The problem is that our sanctification is going to take a long time and the results may be minimal (if noticeable at all) in the short term. We can't give up! We must stand firm.
The question I have is: who is Paul's "true companion"? The NIV text note says that it is probably a guy whose name is Syzgus (which means "companion"). But that seems a bit strange to me that Paul would introduce this loyal or true guy that we've never heard of before. Not impossible, but you'd think if he meant that much to Paul his name would appear elsewhere.