This is an old Viking term and is a nice way to say a person has either died or will be passing soon. When a mighty chief or king died, his body was often placed upon a special bier and then put aboard a long ship. The steering oar was lashed straight, the sails were set, and the war-craft was set loose to sail into the sunset with its sleeping warrior to honor him.

There is also the same version where flaming arrows were shot at the ship as it sailed away with the departed person.