DestinationLabel seems (?) to be a term used in the Material Design docs but when initially onboarding it can be confusing as a concept because they contain more than a simple label. In addition, the property for setting the items in the navbar is labels so it should probably be renamed to items.

DestinationLabel seems to be only used in the BottomNavigationBar but I'm not sure if there is a broader use case I'm missing.

Happy to do a PR if you need.