The notebooks themselves are all numbered and titled; the journal (that is, the idea of the journal) has a proper name.
The first twenty-five notebooks are centered around a keeping-out theme. Think "This is Private Property", "Keep Out", et cetera. I got pretty creative after around ten notebooks.
After #25, I chose quotes. Whether they were deep and philosophical or just funny, the titles held some value to me and usually to the theme of what was happening in my life at the time (even though I titled the notebook before I started writing in it). The current notebook, #54, is titled "The Non-Sober One", and it's based on something one of my friends said about me--basically, how I'm scary enough while sober. It's true.
I don't refer to these notebooks by their titles, though. I started calling the journals Nbook [pronounced N-Book] when I started journaling. Now, though, Nbook has heard enough from me that he has gotten his degree in psychiatry, so he is now Dr. Nbook.