Saturnine

To be gloomy and slow to move is to be saturnine. The word, indeed, does derive from the planet Saturn: the slowest moving planet visible to the naked eye. The planet was associated with Saturn, the king of the Titans--the predecessor of the famous Olympian gods. No doubt the gloomy nature of the word comes not from its divine origin, but more from the association with astronomer's surroundings: the dark.