Godspeed is a wish of good fortune to somebody setting out. Bid him godspeed, godspeed to you, wished them godspeed.
It is archaic and survives mainly in ceremony and in send-offs for dangerous journeys — it was said to astronauts. The speed in it is the old sense of prospering rather than going fast, so it means may God make you prosper. Note that it is written as one word and was originally a whole sentence.
1noungodspeedA wish of good fortune to somebody setting out.
“As the ship left harbour, the crowd on the pier wished the sailors godspeed.”
godspeed is a farewell.
Proto-Indo-European
*speh₁-
English
Godspeed
English, today
godspeed
Godspeed Univerbation of God speed, elliptical for God speed you, where speed carries the archaic sense “help, further, cause to prosper”. Compare God bless, God damn.
Etymology from Wiktionary, CC BY-SA
Practised in A Song of Ice and Fire