The story
From Blackloe + -ist, from the alias of Thomas White (1593–1676), an influential member of the group.
Etymology from Wiktionary, CC BY-SA 4.0.
Blackloist
Today it means: One of a school of dissident English Roman Catholics in the 17th–18th centuries, opposed to ultramontanism and advocating obedience to secular authorities and dogmatic views similar to Jansenism. Full definition →