Literally, it means “old ones.” In cultures that valued age and experience, elders were honored.
The Gospels and Acts mention “the elders of the people” many times, referring the Jewish religious establishment (which rejected Jesus, showing that age does not necessarily bring wisdom).
As Christianity spread, elders became a feature of the congregations. Acts refers to “the apostles and elders” many times as an authoritative body.
Paul and Barnabas, in their missionary travels, appointed elders in each church (Acts 14:23). In 1 Timothy 5 and Titus 1, Paul laid out the moral qualifications for elders.
Elder is a translation of the Greek word presbuteros, the root of our presbyterian.