USA—‘to go Dutch’ (1907): to have every participant pay their own expenses, or share expenses equally—via ‘to go Dutch treat’ (1887), from ‘Dutch treat’ (1873): a meal, etc., at which each participant pays their share of the expenses—from a German practice
UK, 1967—chiefly British—‘bums on seats’: the members of an audience, at a theatre, cinema or other place of entertainment, especially when viewed as a source of income
1763 in French, 1798 in English—from the name of Étienne de Silhouette (1709-67), Controller-General of Finances in 1759—perhaps because he might have invented the portrait in profile obtained by tracing the outline of a head or figure by means of its shadow
‘Sydney or the bush’: all or nothing (1902)—based on the metaphorical opposition between an easy life in the city and a hard life working in the outback, this phrase was apparently originally used by people risking all on the toss of a coin.
British English: a drinking tour of a number of pubs or bars—but first appeared in 1909 with specific reference to an organised form of propaganda consisting in sending a person from pub to pub in order to promote the Conservative cause
‘to plough a lonely furrow’, or ‘one’s own furrow’ (UK, 1901): to carry on without help, support or companionship—French ‘creuser son sillon’ (‘to dig one’s own furrow’, first used by Voltaire): to carry out with courage and perseverance the task undertaken
UK, early 19th century—private property taken from an enemy in war—originally an Anglo-Indian noun, from Hindi ‘lūṭ’, from Sanskrit ‘luṇṭh-‘, ‘to rob’—came to be also used as slang for ‘money’ and to also denote ‘wedding presents’
The phrase ‘boys in the backroom’, or ‘backroom boys’, appeared in the 1920s as a U.S. political term denoting persons exercising a surreptitious influence. The Oxford English Dictionary is therefore mistaken in saying that it originally denoted, in 1941, persons engaged in research.
‘Backward in coming forward’ means ‘reluctant, shy to do something’. The earliest instances that I have found are about funds set up in order to provide aid to soldiers wounded during the Napoleonic Wars.
Bing Crosby popularised ‘pennies from heaven’ in the 1936 film and song of the same name, but the phrase already existed; and Abraham Burstein, rabbi and author, had used ‘pennies falling from heaven’ in The Ghetto Messenger in 1928.