The Encyclopedia Gallifrey is kept in bottles.
No but think about it—how often does the Doctor get to hear Gallifreyan? No one speaks it anymore, no one but him. So of course he hoards the words he has, bottles them up so he can open them up and listen to another person talk about his home. He was always running away when he was young, so keen to get away from the Time Lords and their arrogance and stubborn refusal to change. They’d seemed to constant then, despite everything he learned, despite the greatest rule—that the one constant in the universe is change, that even time itself will run out, that everything dies and everything ends.
Even the Time Lords. Even Gallifrey.
He keeps the words in bottles so late in the TARDIS’s night cycle, when his companions have wandered off to their beds, he can retreat to the silence of the library, close his eyes, and let the words wreath the air around him. For a few moments he can almost smell the breeze blowing down from the mountains, feel the sunlight on his face. For a few moments he is a boy again, in a field of red grass.
And then the words fade into the hum of the TARDIS and the image falters behind his eyes and he is alone, again.