Greek poimēn (shepherd) — translated "pastor" (from Latin pastor, also "shepherd") in Ephesians 4:11, the only place in the NT where the noun is used as a church office title. The corresponding verb poimainō ("to shepherd, to feed, to tend") appears in Jesus' commission to Peter (John 21:16 — "Tend my sheep") and in Peter's instruction to elders (1 Peter 5:2 — "shepherd the flock of God that is among you"). In the NT, shepherd, pastor, elder (presbyteros), and overseer/bishop (episkopos) are three titles for one office — "the overseers, among whom the Holy Spirit has made you to shepherd" (Acts 20:28, Paul to the Ephesian elders).
The NT uses three interchangeable titles for the same office to emphasize three aspects of the work: elder describes the man's character (mature, seasoned, of proven wisdom); overseer describes the authority (he watches, governs, leads); shepherd/pastor describes the posture (he tends, feeds, protects, leads the flock). The shepherd image is dominant across Scripture. God is the Shepherd of Israel (Psalm 23, Ezekiel 34). The coming Messiah is "one shepherd" who will feed His flock (Ezekiel 34:23, Micah 5:4). Jesus is the Good Shepherd who lays down His life (John 10), the Chief Shepherd who will appear (1 Peter 5:4), the Great Shepherd who was raised from the dead (Hebrews 13:20). Human pastors are under-shepherds — accountable to Christ, feeding His flock, not building their own. Peter's charge: "Shepherd the flock of God that is among you, exercising oversight, not under compulsion, but willingly, as God would have you; not for shameful gain, but eagerly; not domineering over those in your charge, but being examples to the flock. And when the chief Shepherd appears, you will receive the unfading crown of glory" (1 Peter 5:2-4). The modern "Senior Pastor as CEO-leader" has largely replaced this biblical picture and impoverished the Church.