Gird Up One's Loins Meaning

Example : 1857, Herman Melville, The Confidence Man, ch. 37:  Man came into this world, not to sit down and muse, not to befog himself with vain subtleties, but to gird up his loins and to work.1920, Lucy Maud Montgomery, Rilla of Ingleside, ch. 9:  Then Susan said briskly, "Well, we must just gird up our loins and pitch in."2004, "Editorial," nepalnews.com (Nepal), vol. 24, no. 6 (Aug 3-19):  King Gyanendra must gird up his loins and prepare himself for all exigencies.