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
USA, 1911: a newcomer—but, from 1903 onwards, as ‘new kid in one’s block’: a child who has recently moved into the block where one lives—‘block’: a group of buildings in a city bounded by intersecting streets on each side
a picture conveys far more than words—USA, 1877, as ‘a picture tells more than printed words’—from 1866 to 1876 the notion had been used with specific reference to pictures by the cartoonist Thomas Nast
to urinate—slang—2nd half of the 20th century—based on the sound /eɪn/, common to the verb, adjective and noun that compose it—‘main vein’ probably refers to the penis
UK, 1884—‘what a surprise!’—a borrowing from French—chiefly used ironically, to imply that a situation or event is unsurprising, typical or predictable
UK, 1794—expresses one’s strong and often petulant inclination to do a particular thing—here, ‘pin’ (i.e., a small, thin, pointed piece of metal) is used of the most trivial or least significant thing