The story
Named after the headquarters of the UK Royal Institute of International Affairs, based in Chatham House, London, where the rule originated in June 1927.
Etymology from Wiktionary, CC BY-SA 4.0.
Chatham House Rule
Today it means: A rule, applied to some controversial debates and discussion panels, stating that anybody who attends is free to use information from the discussion, but cannot reveal who made any comment. Full definition →