The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A form of torture used against suspected rebels during the period of the Irish Rebellion of 1798, in which hot pitch or tar was poured into a conical paper "cap", which was then forced onto the bound suspect's head, allowed to cool, and rapidly removed, taking with it a portion of the skin. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.