From:	Christopher Angel [SMTP:cja124@mail.usask.ca]

Peorth (I think that's the NA spelling) is the Goddess of Forever.  Weird
jurisdiction, since it essentially covers all three of the Norns' areas.

Actually, Peorth being the Goddess of Forever happens to be a fan idea. 
I've never seen it in the manga. What I have heard is that the word Peorth 
means secret or mystery in another language. Can't remember which.