It's fairly plausible that the people working on this specification were unaware of this pre-existing acronym (which ranked after Defense In Depth, when I searched it), and just said "Oh, we're making Distributed IDentifiers. Let's call them DIDs! That's easy to remember."
When used in verbal conversation, is it generally spelled out like CPU (dee eye dee), or said as a word like RAM (did)?
And yet ...
...you've got me wanting to pay attention to something; I'm migrating from a public telco/PTSN job to The world of hosted pbx and managed voice in two weeks and I wonder if that linguistic quirk translates between the two types of environment.
Personally, I think WebAssembly is going to massively revolutionize app delivery. In ten years we will have all but forgotten about JavaScript, switching instead to client-side apps that run at near binary-native speeds, written in real languages with complete type systems.