He looseth the bond of kings - He looseth the authority of kings - the “bond” with which they bind their subjects (Isa 45:1; Gen 14:4; Dan 2:21).
a girdle - the cord, with which they are bound as captives, instead of the royal “girdle” they once wore (Isa 22:21), and the bond they once bound others with. So “gird” - put on one the bonds of a prisoner instead of the ordinary girdle (Joh 21:18).