Mercury was the closest planet to the Sun, or Sol, the star in Earth's Solar System. Despite it's closeness to the sun, Mercury nonetheless had a Space Corps presence. Things or people from Mercury were referred to as "Mercurian".
By the time the DivaDroid Series 4000 mechanoid Kryten left the Solar System, he had been programmed in many off-world eating techniques, including the often lethal "Mercurian boomerang spoon" that originated on Mercury. Three million years later, aboard the Legion Station in Deep Space, Kryten noted his proficiency of this strange utensil to Legion. ("Legion", Series VI)
- Mercury on Wikipedia