The English language is endlessly fascinating. Or endlessly baffling, depending on how you want to look at it. There are so many expressions that, taken literally, make no sense. We all know that the expression 'to steal someone's thunder' means taking credit for something they have done or diverting attention from their achievements. But what are its origins?
The expression is connected not to the weather but to the theatre. The story goes that one John Dennis, largely forgotten except for this anecdote, wrote a play called Appius and Virginia that was set in ancient Rome and in which he needed to create the effect of a thunderstorm; he came up with the idea of rattling a sheet of tin. The play, performed at Drury Lane in London in 1709, was not a success and the management quickly withdrew it.
However, Dennis, the mostly unsuccessful playwright, subsequently attended a performance of Shakespeare's Macbeth in which the various storms were created using his technique of rattling a sheet of tin. Deeply incensed, he cried out, ‘Damn them! They will not let my play run, and yet they steal my thunder!’
The actual words are in doubt and are also reported as "That is my thunder, by God; the villains will play my thunder but not my play!". What is clear is that Dennis's experience was the source of this attractive little phrase.
The expression can now be used to cover any set of circumstances in which someone is overshadowed, usually unjustly.