UK, 1871—a paper bag, balloon, etc., filled with flour and thrown or dropped such that it bursts and disperses its contents over the target on impact, usually as a prank or as part of a protest or public demonstration
UK, 1884—‘what a surprise!’—a borrowing from French—chiefly used ironically, to imply that a situation or event is unsurprising, typical or predictable
a cake made with the ingredients available during wartime—first used during the First World War (1914-1918)—came back into usage during the Second World War (1939-1945)
Australia, 1934—an inexhaustible supply of something, especially money—alludes to The Magic Pudding (1918), by Norman Lindsay, in which a pudding instantly renews itself as it is sliced or eaten into
UK, 1911—a sharp blow to the back of the neck—refers to the practice of killing rabbits in this way, and originated in boxing—Australia, 1913: ‘rabbit killer’, also ‘rabbit-killer punch’
a person exercising an insidious or corrupting influence, especially over a ruler, government, etc.—UK, 1917—refers to Grigori Efimovich Rasputin (circa 1869-1916), mystic and influential favourite at the court of Tsar Nicholas II