From a more practical sense, the naming is most likely to stay unchanged just because a lot of people are used to already.
But the concept as it applies to HTTP APIs is a great one that I think could have a broadly recognized implementation. Whether folks start adopting the "Idempotency-Key" header or some other approach, having awareness and maybe even a standard could be great.
Oh yes, hugely agree there! Part of the reason that I wrote this is that I couldn't find much prior art around idempotency keys (there is some, but not much). I am at least partially hoping that people will remember this article (or that it'll show up in a Google search) as they're implementing their own similar concept, and re-use the naming.