Why was "tantrum" trending last week?
mid-15c., "pacification," from Middle French apeisement, Old French apaisement "appeasement, calming," noun of action from apaisier (see appease). First recorded 1919 in international political sense; not pejorative until failure of Chamberlain's policy toward Germany in 1939 (Methods of appeasement was Chamberlain's description of his policy).
A political policy of conceding to aggression by a warlike nation.
Note: A classic example of appeasement is the Munich Pact of 1938, negotiated between Neville Chamberlain and Adolf Hitler. Chamberlain, the prime minister of Britain, allowed Hitler to annex part of Czechoslovakia to Germany.