What does "dak" mean?

Dak: Post; mail; also, the mail or postal arrangements; -- spelt also dawk, and dauk. [India] Dak boat, a mail boat. Percy Smith. -- Dak bungalow, a traveler's rest-house at the and of a dak stage. -- To travel by dak, to travel by relays of palanquines or other carriage, as fast as the post along a road.