When a person complains about someone else “stealing their thunder”, their meaning is somewhat obvious. Each of has our special ideas, knowledge, or skills that we can display, and when someone else upstages us by co-opting those things themselves, they steal our moment — our chance to catch everyone’s attention. “Stealing someone’s thunder” is very easy to understand on an intuitive, figurative level. So it may be somewhat surprising in the phrase’s origin, the thunder is meant literally. The playwright John Dennis wrote a play call Appius and Virginia. During its production, Dennis came up with an ingenious invention to simulate the sound of thunder, and it was used to great effect during the play. The rest of the play, though, was less well-received and its run in the theater was painfully short. When Dennis attended a showing of Macbeth in the same theater some time later, he was appalled to hear that same thunder noise, one that could only have been made by his machine, during the production. Dennis is said to have exclaimed, “Damn them! See how the rascals use me! They will not let my play run, and yet they steal my thunder!”
– A few thoughts from your friend Saxo