Papist
Definition: a derogatory term for Catholics
The idea behind this is to refer to someone who follows the Pope (“papal”) more than God or Jesus Christ.
Why I Looked It Up
From What’s Bred in the Bone:
The religion of the School, for instance; it was a kind of middle-brow Anglicanism, not too heavily stressed because the School contained boys of all denominations, including several Jews, and some richly coloured boys from South America, who were probably Papists.