It was also a term referring to those that were older in age, who more often than not were the leaders of the church. This was not always the case. Timothy for example was a pastor at a young age. He was a partaker of the glory that shall be revealed. It is exactly the same command given to him by Jesus himself in the 21st chapter of John.
Sheep have a right to be fed.
Take full responsibility for the care, teaching, development, and safety of the flock. Note greedy for money, but eager to serve. Go not from house to house. Leaders are exhorted not to lord over those entrusted to them but to be examples. Let no man despise thee.