A couple of years ago, while backpacking with some guys in the 100 Mile Wilderness of the Appalachian Trail in Maine, I was—we were—having a really hard go of things. The trail was harder than what we were used to, and we were tired and discouraged. Then we saw coming toward us from the opposite direction a solitary hiker. Tall and lanky, no backpack but just a fanny pack, he stopped and smiled and pulled bananas and hard candy out of his pack for us.
He was what we call a “Trail Angel,” someone out on the trail to help distance hikers. We chatted for a moment, and I asked his “trail name.”
“Onesimus,” he replied.
“Oh,” I said, “I think you are pretty useful.”
His face lit up, and he said, “You’re a brother!” We chatted a bit more before we moved along, for we had “miles to go before we [could] sleep” that day.
Onesimus, you see, means “useless.” Paul is making a play on words in his letter to Philemon whose slave “Useless” had run away and found Paul. Paul was pointing out that Onesimus was anything but useless. As a brother in Christ, he was indeed useful.