2 Corinthians 8:22

‘And we have sent with them our brother, whom we have many times proved earnest in many things, but now much more earnest, by reason of the great confidence which he has in you.'

And along with these two men Paul has also sent a third person, a man whose earnestness in many ways he can vouch for, and who is especially earnest in his desire to be of benefit to the Corinthian church because he has such a high view of them. This may signify that he was also helping administer the Collection, and was confident of the Corinthian's generosity, or that he had come to provide them with sound spiritual ministry. Or even both.

If Paul had forgotten the first man's name this further non-mention of a name might indicate a tactful touch which would ensure that the first unknown did not feel slighted. On the other hand the non-mention of names may indicate Paul's unwillingness to give his personal Apostolic backing to people whom he himself had not appointed. See the next verse.