There were questions tagged "dd-essentials." We had determined that D&D should be abbreviated "dnd", and also I think it's worth saying it's D&D 4.0 Essentials since there well may be a D&D 5.0 Essentials in 2020. Go vote on my tag synonyms if you agree, I think it should be changed to "dnd4.0-essentials" and I've retagged the existing questions to that end.
Changing the dd to dnd is definitely the way to go. I'm not so sure about the 4.0, though... The product's name is "D&D Essentials", so dnd-essentials or dnd-essentials4.0 would be a more discoverable tag I think.
On the other hand, dnd4.0-essentials is more filterable... shrug
"Yea" for changing it to [dnd-essentials]. That just looks like an oversight.
"Nay" for trying to read the minds of future Wizards development teams. We should tag it what it's called, and worry about differentiating it from non-D&D4e Essentials if and when such a thing exists. If it ever matters, we can set up a quick synonym then to fix things up.