It's Latin actually! It's from the Aeneid, when Aeneas visits the Underworld and hears all about how awesome his descendants will be (as one does, I guess)--he and his guide leave through one of two gates out of the Underworld:
There are twin gates of sleep, or which one is made of horn,
through which an easy exit is given to true shadows/dreams;
the other, made with ivory, shines,
but the Shades send false dreams toward the skies (through it).
(or something like that, anyway) And then Aeneas leaves through the gate of ivory, which is the false gate, so there is all this debate about what that means. But I just really like the image and the lines.
Also, your signature! Where is it from? I really like it because the best thing about the best books on fairyland--even the kids' books--make it dangerous and really wild, you know? As it should be.