How does the word saturnine derives !

How does the word saturnine derives ! if you care why words derive ! Saturnine might have had originated in the fact that Saturn’s Equinoxes are month long darkness (lack of sunshine for weeks altogether) as Saturn tilts away from sun (and toward sun) for 90 degree (Earth’s 23.44 degree only) ! Thats means parts of sun will get no sun-light for several weeks in the culmination of these Saturnine equinoxes. So saturnine means a person who is gloomy or melancholic. ( — perhaps at-least for longer duration.) I learned this because I was playing with words when grammar of my computer showed the word and I checked its meaning, I was although writing about equinox of Saturn, I came to learn this, cool is it?