I'm enjoying Saint Brigid's Bones so far (on p. 84). One thing bumped me out of the story, however, because it felt anachronistic: on p. 72 Dierdre describes her dream of being freezing cold and Dari sarcastically says "Obviously Brigid wants us to go to the North Pole". Was the North Pole a concept that was known in this period?
A great question. Yes, any educated person in the ancient or medieval world knew about the North Pole. From the time of the early Greeks, everyone knew the earth was a sphere and that it was colder the farther north you went. The idea that people in the Middle Ages thought the earth was flat is a modern myth.