Gollum's name for the Sun.
For long centuries, Gollum had hid with his Precious - the Ring - in the darkness beneath the Misty Mountains. When he lost the Ring to Bilbo Baggins, he emerged at last to hunt for it, but after those long lightless years, he could hardly stand the light above the ground. He came to hate the Moon, which he called the White Face. Most especially, though, he shunned the Sun, which to him was a scorching Yellow Face, and hid from it in shadow, or under cover of night, whenever he was able.