Gemini
the twins constellation
Today this word meansThe constellation with two bright stars side by side. Also the name of America's second crewed space program.
The two stars are named, simply, Castor and Pollux.
The tale of one twin mortal and one immortal, taking turns in the sky day by day, was read into the way the two stars rise and set together.
The spacecraft carried two astronauts — hence the program's name, Gemini.
Worth noting
The word gemini itself is just Latin for "twins." The story attached to the constellation is that of the Dioscuri.