The greek word for "servant" is huperetes.

Huperetes is a compound word of huper (under) and erreso (to row). It often refers to someone who serves with his hands. Paul was under Christ,  being used by Him to pour out the word of God.


A similar usage is found in Luke:
Just as they were handed down to us by those who from the beginning were eyewitnesses and servants of the word, (Lk. 1: 2)