What does it mean for Jesus to ”Gird his Loins?”

The expression "gird your loins" comes up a number of times, most notably in the account of the Passover. Israel must be ready to be on the move, to get to work, at the moment the Lord commands. It makes sense, then, when Jesus tells his disciples to gird their loins. They too must be vigilant and ready to get to work, waiting for his arrival and command. But for Jesus to gird his loins? This means that the master has become the servant.