'Whether Mr. Dennis was the inventor, of that improvement [of making stage thunder 'by troughs of wood with stops in them']I know not; but it is certain that being once at the tragedy of a new author with a friend of his, he fell into a great passion at hearing some, and cry'd, "'Sdeath ! that is my Thunder! "'(Alexander Pope, The Dunciad (1729), Bk. ii, 1. 218 n.) The accepted modern version is 'Damn them! They will not let my play run, but they steal my thunder. ' (Walsh, Handybook.)
Note from John Dennis, from Literary Anecdotes