bemoan - Not that Moab deserves pity, but this mode of expression pictures more vividly the grievousness of Moab’s calamities.
all ye that know his name - those at a greater distance whom the fame of Moab’s “name” had reached, as distinguished from those “about him,” that is, near.
strong staff ... rod - Moab is so called as striking terror into and oppressing other peoples (Isa 9:4; Isa 14:4, Isa 14:5); also because of its dignity and power (Psa 110:2; Zec 11:7).