The word “Godspeed” is used to wish a person well, typically as they depart on a journey. It is appropriate to use in the context of parting, so you can say “godspeed” to bid someone goodbye, in the same way as you might use “bon voyage” or “farewell.”
“Godspeed” dates back to the 15th century, according to Merriam-Webster, and has its origins in Middle English, a version of English spoken between the years 1150 and 1500. The original appearance of “godspeed” would have been along the lines of “god speid” or “God spede you,” voiced with the intent of wishing someone a successful and prosperous journey. Spellings varied significantly in Middle English, notes Philip Durkin of the Oxford English Dictionary, but the spelling of the word became standardized as "godspeed."