Saturnine comes from the planet Saturn and the Roman god whose name it bears. In Roman mythology, Saturn was the oldest and most somber of the gods, and the planet named after him was the most distant, slowest, and coldest-looking of the planets then known. Medieval astrology held that anyone born under Saturn's influence would have a dark, heavy, gloomy temperament. So the word saturninus ("of Saturn") came to mean "gloomy, morose." It forms the exact opposite pair to the cheerful jovial (of Jupiter) seen earlier.