It doesn't have a peculiar name. It is just a trade in that example. This however is called a deflection:
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So, my plan worked, but 24. Qd4 could have been played. Looking past that, how would you label the rook on e2? I knew if I removed that, I could go for the mate. So the rook is like a defender, but it's not just defending a piece. It is defending/preventing mate. What do you call this? Remove the mate preventer?