It's of interest to me, that "The Deep" was a term used in reference to the Babylonian goddess, Tiamat, in the Enuma Elis. Basically, it's a Babylonian creation myth, and relates the story of the god Marduk's cunning and victory over Tiamat, and his creation of mankind. Coincidentally, Tiamat was often portrayed as a serpent or dragon, along with her children. Maybe these references are coincidental; maybe not... After all, the lore does contain many references to "the deep" and "dragons". Going to do a bit of reading and see what I can find.