>stated "latrinalia" was a recent coinage, but regrettably did not give date.

I only just found this thread now, searching for latrinalia relating to the new graffiti thread; but here is the poop on the coinage of this. Professor Dundes was the real deal in folklore and anthropology and developed a field of study in latrinalia, which he called (per force) 'latrinology'.

Here I Sit—A Study of American Latrinalia. Papers of the Kroeber Anthropological Society (1966)

here's his CV (in pdf format): http://ls.berkeley.edu/dept/anth/dundes.cv.pdf