Stealing thunder
Stealing thunder is to take someone else's idea, using it for one's own advantage or to pre-empt the other party. Origin. The idiom comes from the peevish dramatist John Dennis early in the 18th century, after he had conceived a novel idea for a thunder machine for his unsuccessful 1709 play "Appius and Virginia" and later found it used at a performance of "Macbeth". There is an account of it in "The lives of the poets of Great Britain and Ireland" by Robert Shiels and Theophilus Cibber: Rhetorical use. In a contentious situation, such as  a court case, political debate or public relations crisis, it is a tactic used to weaken the force of an adverse point. By introducing the point first and being open about it or rebutting it, the force of the opposition's argument is diminished – their thunder is stolen.