Issue 2 mentions that Terim is a northern god.
Dave Sim Speaks
"As I recall, the two different spellings of Terim and Tarim were accidental at first, in the same was that I had trouble bearing in mind that Cerebus was supposed to refer to himself in the third person and would later cover for it by saying that he referred to himself as 'I' when he had been around the civilized areas too long. I was covering for not remembering how to spell Tarim by making it the masculine version of the deity's name."
"Cirin is attempting to revive the worship of the Single Goddess - Terim, preaching that Tarim is a bastardization of the original deity. The Kevillists disagree, but we're getting to that. This is why genuinely antiquitous references (like the Spheres of the Gods are always to Terim (with an "e"). It's my way of showing I agree with Cirin, even though she might be wrong."