woch'-man (tsopheh, shomer, metsappeh, notser): Used to designate a sentinel on the city walls (2Sa 18:25; 2Ki 9:18; Ps 127:1; Isa 62:6) or on the hilltops (Jer 31:6). Song 3:3; 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: Jer 4:16, "watchers"), while shomer also embraces the idea of "defending" or "guarding." In Isa 21:6 metsappeh is to be taken generally in the sense of "watch." In Sirach 37:14 skopos, means simply "looker."
W. M. Christie