[Griff]

Godspeed

The modern word godspeed derives from the expression God speed you on your way, which came about at a time when speed meant to prove successful or to prosper. That archaic sense of speed is long gone, but godspeed still means may you prosper on your way. It’s similar to good luck, though it’s often used in reference to people who have passed away. It’s also sometimes said to people, especially sailors, embarking on difficult journeys.

The term, which functions as both a noun and an interjection, is sometimes treated as two words, but the one-word godspeed is about five times as common in modern writing. Some publications always capitalize the g in godspeed, and some don’t.

http://grammarist.com/usage/godspeed/

This is interesting because it seems like I've seen it
misused in period movies.