Watchman woch'-man (tsopheh, shomer, metsappeh, notser): Used to designate a sentinel on the city walls (2 Samuel 18:25, 2 Kings 9:18, Psalms 127:1, Isaiah 62:6) or on the hilltops (Jeremiah 31:6). Song of Solomon 3:3, Song of Solomon 5:7 introduces another class, "the watchmen that go about the city," and thus, it would seem, points to some system of municipal police. The distinction in meaning between the various words is clear, tsopheh having the idea of "outlooker" and notser that of "careful watcher" (being applied even to besiegers from outside: Jeremiah 4:16, "watchers"), while shomer also embraces the idea of "defending" or "guarding." In Isaiah 21:6 metsappeh is to be taken generally in the sense of "watch." In Wisdom of Sirach 37:14 skopos, means simply "looker."
W. M. Christie