I agree readily that glyph isn't common. It has a few meanings, but it seems to be used almost entirely in quite technical contexts. It will be treated as rare from now on.
But the idea of polytheism being rare surprises me a little. I would have thought most people would have come across terms like polytheism (belief in multiple gods), monotheism (belief in one god), atheism (belief in no god), along with, perhaps pantheism (belief in god as embodied in the whole universe, or the acceptance of all gods from all religions) and plain old theism (any belief in one or more gods). All these words are currently treated as common, and I'm inclined to leave that situation as it is. Anyone have any comments?