"to gird one's loins".

Gird (< ME girden < OE gyrdan 'to gird, bind round; L. cingere') is related to girdle. The concept behind girding is to encircle or put on a belt. Loins weren't the only things being girded in the Old Testament: cf. Lev VIII.7. And he put upon him the coat, and girded him with the girdle, and clothed him with the robe, and put the ephod upon him, and he girded him with the curious girdle of the ephod, and bound [it] unto him therewith.

Ceci n'est pas un seing.