I think Key is standard term in DI context. Everyone knows what a binding key is in that context.

One more framework where this concept is called Key (http://pythonhosted.org/injector/).

If somebody mentioned AnnotatedType in context of DI, I'd have no clue what it is nor what it's it's purpose. On the other hand, if somebody mentions key, or binding key, I immediately  know what they are talking about....