ke (maphteach, an "opener"; compare kleis, "that which shuts"):
Made of wood, usually with nails which fitted into corresponding holes in the lock, or rather bolt (Judges 3:25). Same is rendered "opening" in 1 Chronicles 9:27.
Used figuratively for power, since the key was sometimes worn on the shoulder as a sign of official authority (Isaiah 22-22). In the New Testament it is used several times thus figuratively: of Peter: "the keys of the kingdom of heaven" (Matthew 16:19); of Christ, in Revelation, having the "keys of death and of Hades" (Revelation 1:18), also having "the key of David" (Revelation 3:7). An angel was given "the key of the pit of the abyss" (Revelation 9:1; 20:1). our Lord accused the teachers of the law of His day of taking away "the key of knowledge" from men, that is, locking the doors of truth against them (Luke 11:52; compare Matthew 23:13).
Edward Bagby Pollard