‘not under any circumstances’—Royal Air Force slang, 1942—short for ‘not on your Nelly Duff’, i.e., ‘not on your life’, ‘Nelly Duff’ being rhyming slang for ‘puff’ as used colloquially in the sense of ‘life’
USA, 1900: to get a stage act ready—Canada, 1961: to organise oneself to undertake or achieve something—from ‘to get together’ (i.e., to organise, put in order, harmonise)
Canada, 1928—resembling Jeeves, the perfect valet in stories by the English author Pelham Grenville Wodehouse (1881-1975); this fictional character first appeared in 1915
an impressive person or thing, viewed as being difficult to rival or surpass—USA, 1912, in reference to the difficulty faced by an entertainer coming on stage immediately after a popular or successful act
late 19th century—to disappear suddenly without leaving information about one’s whereabouts—from conjuring, in which ‘vanishing act’ designates an act of making a person or thing disappear as if by magic, and an act of disappearing in this manner
Australia, 1943—a foolish or silly person—from the synonymous noun ‘dill’ (1933), itself apparently a back-formation from the adjective ‘dilly’, meaning ‘foolish’, ‘silly’
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.