Porphyry was a philosopher whose now-lost works attacking Christianity were quoted by Saint Fidgeta's teacher, Putricordes (Saint Fidgeta and Other Parodies; 11). A wax tablet preserved in Santa Fidgeta originating from Fidgeta's school includes her name and the phrase "Jocus Porphyrias."
Inspiration
A rock consisting of crystals embedded in a compact dark red or purple groundmass[1]. Like other semiprecious stones (cf. jade, jasper), it has been used as a person's name, including a Greek scholar and philosopher (c.232-c.304) who wrote extensively against Christianity[2]. Suggests Charles Bowen: "John was calling on his personal encyclopedia of odd facts for this one.[3]"
Not to be confused with porphyria, a disease so named for bodily discolorations purple in color[4].
As jocus is Latin for “joke”[5], the translation is thus "joke of Prophyris.”