UK—a ball game for three players, in which the middle player tries to intercept the ball as it passes between the other two—hence: a person, party, etc., caught between others in a conflict, dispute, etc.
UK, 1915—a female worker in a munitions factory, especially during the First World War (1914-18)—from ‘munition’ and the suffix ‘-ette’, denoting women or girls linked with, or carrying out a role indicated by, the first element
USA, 1986—consent by nearby residents to the siting of something despite the fact that they perceive it as unpleasant or hazardous—acronym from ‘yes in my back yard’, after ‘NIMBY’
Australia, 1865 (nonce-use): the process of turning into a person of high social rank—UK, 1964 (coined by sociologist Ruth Glass): the process whereby middle-class people take up residence in a traditionally working-class area of a city
New York City, 1896—a lawyer who seeks accident victims as clients and encourages them to sue for damages—refers to lawyers, or their agents, following ambulances taking accident victims to hospital, in order to gain access to those victims
to be utterly defeated—alludes to the defeat of Napoléon I at the Battle of Waterloo in 1815—UK, 1832, as ‘to meet with a Waterloo’—USA, 1838, as ‘to meet one’s Waterloo’
chiefly UK politics—a culture characterised by influential networks of close friends—from ‘chum’ (a close friend) and ‘‑ocracy’ (forming nouns designating forms of government or groups who exercise political or social power)
(literally) to formally agree to something by signing an official document—(figuratively) to make a firm commitment about something—USA, 1900s, in reference to life-insurance contracts
highly convincing circumstantial evidence—USA, 1862—ascribed to Henry David Thoreau—refers to the practice of surreptitiously diluting milk with stream-water