What is "god speed you"

Speed \Speed\, v. t.

1. To cause to be successful, or to prosper; hence, to aid; to favor. ``Fortune speed us!''
   --Shak.

   With rising gales that speed their happy flight.
   --Dryden.

2. To cause to make haste; to dispatch with celerity; to drive at full speed; hence, to hasten; to hurry.

   He sped him thence home to his habitation.
   --Fairfax.

3. To hasten to a conclusion; to expedite.

   Judicial acts . . . are sped in open court at the instance of one or both of the parties.
   --Ayliffe.

4. To hurry to destruction; to put an end to; to ruin; to undo. ``Sped with spavins.''
   --Shak.

   A dire dilemma! either way I 'm sped. If foes, they write, if friends, they read, me dead.
   --Pope.

5. To wish success or god fortune to, in any undertaking, especially in setting out upon a journey.

   Welcome the coming, speed the parting guest.
   --Pope.

   God speed you, them, etc., may God speed you; or, may you have good speed.

   Syn: To dispatch; hasten; expedite; accelerate; hurry.